THE ROLE OF CHELATE COORDINATION COMPOUNDS OF BIOGENIC METALS IN THE VITAL ACTIVITY OF PLANTS
The review article discusses the main issues of creating and using modern chelated microfertilizers based on trace elements in agricultural production. Issues of the role of microelements in the vital activity of living organisms and methods of overcoming the lack of microelements in plants are hig...
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2023
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| author | Trunova, Olena |
| author_facet | Trunova, Olena |
| author_institution_txt_mv | [
{
"author": "Olena Trunova",
"institution": "V.I. Vernadsky Institute of General and Inorganic Chemistry NAS of Ukraine"
}
] |
| author_sort | Trunova, Olena |
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| description | The review article discusses the main issues of creating and using modern chelated microfertilizers based on trace elements in agricultural production. Issues of the role of microelements in the vital activity of living organisms and methods of overcoming the lack of microelements in plants are highlighted. An overview of coordination compounds of 3d-metals (Fe, Mn, Zn, Cu, Co, Ni, Mo) with different classes of complexons, features of their structure and properties is presented. It contains relevant material on the use of microelement complexes for the creation of modern chelated fertilizers. Attention is paid to the use of trace elements complexonates in areas contaminated with radionuclides (137Сs, 90Sr). |
| doi_str_mv | 10.33609/2708-129X.88.12.2022.91-138 |
| first_indexed | 2025-09-24T17:43:48Z |
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91
UDK 541.49: 546.72+ 546.73 + 546.74 + 546.47+ 581.133.8+632.121– 54-386 doi: 10.33609/2708-129X.88.12.2022.91-138
THE ROLE OF CHELATE COORDINATION COMPOUNDS OF BIOGENIC
METALS IN THE VITAL ACTIVITY OF PLANTS.
O. K. Trunova*
V.I. Vernadsky Institute of General and Inorganic Chemistry
of the National Academy of Sciences of Ukraine,
32/34 Academic Palladin ave., 03142 Kyiv, Ukraine
*e-mail: trelkon@gmail.com
The review article discusses the main issues of creating and using modern chelated micro
fertilizers based on trace elements in agricultural production. Issues of the role of microele
ments in the vital activity of living organisms and methods of overcoming the lack of micro
elements in plants are highlighted. An overview of coordination compounds of 3d-metals (Fe,
Mn, Zn, Cu, Co, Ni, Mo) with different classes of complexons, features of their structure and
properties is presented. It contains relevant material on the use of microelement complexes
for the creation of modern chelated fertilizers. Attention is paid to the use of trace elements
complexonates in areas contaminated with radionuclides (137Сs, 90Sr).
Keywords: coordination compounds, microelements, chelates, complexones, fertilizers,
plants.
INTRODUCTION. It is possible to elimi
nate pathological phenomena caused by a de
crease in the level of biometals in plants by in
troducing trace element additives into the soil
in a form that is easily transported and assimi
lated by living organisms. In recent years, the
interest of scientists in the creation of effective
and environmentally safe growth regulators
has increased: the development of methods of
their synthesis, the mechanisms of action and
methods of application are being studied.
The role of microelements (МЕ) in the life
activity of living organisms is well known. Pa
thology associated with the lack of ions such
as iron, zinc, manganese, copper, cobalt, zinc
leads to various functional diseases, impaired
metabolism, possibly to the death of animals,
reducing productivity and crop yields [1–6].
Мicroelements are involved in such important
biochemical processes as respiration, photo
synthesis, protein synthesis, blood formation,
protein, carbohydrate and fat metabolism, hu
mus synthesis. Due to their catalytic action,
microelements allow plants to more effectively
use the main nutrients – solar energy, water and
macroelements - nitrogen (N), phosphorus (P)
92 ISSN 2708-129X. Укр. хім. журн., 2022
THE ROLE OF CHELATE COORDINATION COMPOUNDS OF BIOGENIC METALS IN THE VITAL ACTIVITY OF PLANTS.INORGANIC CHEMISTRY
and potassium (K), which, in turn, has a po
sitive effect on plant productivity and harvest
quality. Microelements are able to strengthen
the ability of plant tissues to recover, which
significantly reduces damage to plants by di
seases. Most trace elements are active catalysts
of biochemical processes in plants. In addition,
trace elements affect the direction of biochem
ical reactions in plants due to their influence
on plant biocolloids. Microelements cannot
be replaced by other substances and their de
ficiency must be filled taking into account the
form in which they will be in the soil. Plants
can use trace elements only in water-soluble
form (mobile form of trace element), and the
immobile form can be used by the plant after
complex biochemical processes involving soil
humic acids.
The main role of trace elements in increas
ing the quality and quantity of the crop is as
follows:
1. In the presence of the required amount
of trace elements, plants have the ability to
synthesize a full range of enzymes, which will
allow more intensive use of energy, water and
nutrition (N, P, K) and, accordingly, to obtain
a higher yield.
2. Microelements and enzymes based on
them strengthen the regenerative activity of
tissues and prevent plant diseases.
3. Microelements are one of the few sub
stances that increase plant immunity. Their
lack creates a state of physiological depression
and general susceptibility of plants to parasitic
diseases.
That is why today there is a need to create
and use new environmentally friendly effective
trace element compounds, both in plant and
animal production, which are lacking in soils
and rations, in order to increase plant yields,
improve animal productivity and the quality of
plant products . Therefore, the creation of new
non-toxic and effective drugs that contribute
to the successful resolution of urgent issues
in some sectors of agriculture is an important
task for agro-industrial complexes around the
world.
BIOLOGICAL ROLE OF METALS. The most
important microelements in plant life are iron,
copper, zinc, manganese, magnesium, cobalt,
molybdenum, which, according to their im
portance in living organisms, can be placed in
the order Fe>Mn>Zn>Cu>Со>Ni>Cr>V>Mo.
Boron, magnesium, calcium are classified
as mesoelements, since for the life activity
of plants, they are required in much more
amounts than microelements.
The physiological significance of the main
trace elements for plants is given in Table 1.
Iron plays a leading role among all me
tals contained in plants. Organic compounds,
which include iron, are necessary in biochemi
cal processes that occur during respiration and
photosynthesis, which is explained by a very
high degree of their catalytic properties. The
catalytic effect of iron is related to its ability to
change the degree of oxidation. The іron ion
is oxidized and reduced relatively easily, there
fore iron compounds are carriers of electrons
in biochemical processes. The process of elec
tron transfer is the basis of the reactions that
occur during plant respiration. This process is
carried out by enzymes – dehydrogenases and
cytochromes containing iron. Among other
processes, the influence on the formation of
the structure and functioning of chloroplasts,
as well as the synthesis of chlorophyll, should
also be noted [7].
93https://ucj.org.ua
O. K. Trunova UCJ № 12 / Vol. 88
Table 1.
Physiological significance of the main microelements in plants.
МЕ Functions in plants Symptoms of deficiency
and its consequences
Plants prone
to deficiency
Fe • A necessary component of many
enzymes in plants. • Is contained in
chloroplasts and takes part in the
photosynthesis and metabolism of N
and S. • The main component in the
synthesis of chlorophyll.
• Can stimulate chlorosis, which appears on
young leaves due to low mobility of Fe in the
plant. • In cereals, chlorosis manifests itself
in the form of interspersed yellow and green
stripes along the leaf.
• Fe deficiency often causes shoot dieback.
Citrus, fruit trees,
vineyards, legumes,
corn, tomatoes, ros
es and ornamental
plants
Mn • necessary for normal photosynthe
sis, • participates in the reduction of
CO2, • plays a role in maintaining the
structure of chloroplasts. • partici
pates in the synthesis of vitamin C
• Violation of the ratio of elements of natu
ral nutrition, • occurrence of point chlorosis,
• sometimes complete absence of fruiting
Оats, barley, beets,
beans, tomatoes, ap
ple trees, roses
Zn • Catalyst in many enzyme systems.
• As part of enzymes, it participates
in the metabolism of starch and nit
rogen.
• Metabolism of carbohydrates, phos
phates and proteins; formation of
growth hormones auxins, DNA, ri
bosomes.
• growth retardation - shredding
• short internodes
• interveinal chlorosis
• brown spots on upper leaves
• deformed leaves and fruits
Corn, hops, beans,
flax, green vegetables,
citrus fruits, grapes,
apples and pears
Cu • Mainly in the composition of pro
teins in green cells, responsible for
binding solar energy. • Along with
Zn, activates an enzyme that prevents
the destruction of plant cells. • Par
ticipates in the process of protein and
carbohydrate metabolism
• Chlorosis and curling of leaves due to dying
of their tips. • Weakened ovary in cereals -
drop in yield in the absence of visible signs
of deficiency. • Reduced release of pollen
grains, which leads to less pollination of flo
wers and reduced yield. It causes "hanging" of
tree crown branches and laying of cereals (low
yield).
Cereals, citrus fruits,
apple trees, pears,
green vegetables,
rice, alfalfa.
Co •A component of vitamin B12, neces
sary for nitrogen fixation in plants •
increases the intensity of respiration
and photosynthesis, contributing to
the formation of chlorophyll and re
ducing its decay in the dark
• Poor growth can be corrected by using am
monium and nitrate nitrogen.
• Manifestation of chlorosis on the leaves.
• Slow plant growth
• Development cycle lags behind the norm.
Beans, peas, clover,
alfalfa
Мо •Provides plants with nitrogen
• participates in hydrocarbon ex
change, in the exchange of phospho
rus fertilizers, in the synthesis of vi
tamins and chlorophyll, • affects the
intensity of redox reactions
• the edges of the leaves acquire an orange, red
or pink shade
• Plant growth is inhibited, leaves are de
formed and die prematurely.
• nitrates accumulate and nitrogen metabo
lism is disturbed - the content of ascorbic acid
decreases. • violations of the phosphorus me
tabolism of plants are observed.
soybeans, grain and
leguminous crops,
clover, perennial gra
sses
94 ISSN 2708-129X. Укр. хім. журн., 2022
THE ROLE OF CHELATE COORDINATION COMPOUNDS OF BIOGENIC METALS IN THE VITAL ACTIVITY OF PLANTS.INORGANIC CHEMISTRY
To activate the process of iron up take by
the plant, a biochemical adaptation of the pri
mary metabolism is necessary, which requires
primarily changes in energy consumption in
the form of macroergic compounds, which
are represented in the cell by such basic forms
as nicotinamate (NADadenine) dinucleotide
phosphate and adenosine triphosphate. In the
course of the development of any organism,
the most important role in providing cells with
these components belongs to mitochondria,
since for adaptive reactions, the effect of iron
deficiency on these qi organelles is impor
tant [8].
A high degree of mitochondrial sensitivity
in this aspect can be explained by the high need
for iron to maintain the activity of metalloen
zymes, iron-sulfur proteins and cytochromes,
thanks to the work of which protons and elec
trons, ultimately, are transferred to the oxygen
in the air. Electron carrier proteins include
iron-sulfur proteins (Fig. 1), containing frag
ments of the (Fe-S)n ferredoxin cluster. In
them, iron is tetrahedrally surrounded by sul
fur atoms of thiolate fragments of cysteine. In
addition to cubic clusters of the type [4Fe - 4S],
larger ones are also known: [8Fe – 7S] and
[Mo-7Fe-8S-X] (in nitrogenase).
Fig. 1. – A fragment of the iron-sulfur protein
structure (Cys is a cytein residue).
Iron is necessary for the synthesis of cyto
chromes, pyridoxine and other iron-sulfur
proteins, components of the reaction centers of
the chloroplast photosystem, cytochrome oxi
dase, catalase, peroxidase and other enzymes
that play key roles in the main physiological
processes – photosynthesis, respiration, nitro
gen fixation and metabolism.
Iron has a special function – indispensable
participation in the biosynthesis of chlorophyll.
Therefore, any reason that limits the availabili
ty of iron for plants leads to serious diseases, in
particular to chlorosis. When photosynthesis
and respiration are impaired and weakened as
a result of the insufficient formation of orga
nic substances from which the plant's body is
built, and the lack of organic reserves, a general
metabolic disorder occurs. Therefore, with an
acute lack of iron, the death of plants inevitably
occurs. In trees and shrubs, the green color of
the apical leaves disappears completely, they
become almost white, and gradually dry up.
Manganese is absorbed by plants and dis
tributed among their organs as a result of meta
bolic processes. Passive adsorption takes place,
especially at high and toxic levels of its content
in the solution. Manganese is distinguished by
a high degree of absorption activity and rapid
transfer in plants. In plant fluids and extracts,
it is present in the form of free cationic forms
and is transported in plants in the form of Mn2+,
and its significant concentrations are found in
young plant organs. One of the most important
functions of manganese is participation in redox
reactions. Mn2+ is a component of two enzymes:
phosphotransferase and arginase. In addition, it
can replace magnesium in other enzymes and
increases the activity of some oxidases. The lat
ter happens, apparently, as a result of a change in
the valence of manganese.
3
metabolism yield).
Co •A component of vitamin B12,
necessary for nitrogen fixation in
plants • increases the intensity of
respiration and photosynthesis,
contributing to the formation of
chlorophyll and reducing its decay
in the dark
•Poor growth can be corrected by using
ammonium and nitrate nitrogen.
• Manifestation of chlorosis on the leaves.
•Slow plant growth
• Development cycle lags behind the norm.
Beans, peas,
clover, alfalfa
Мо •Provides plants with nitrogen
• participates in hydrocarbon
exchange, in the exchange of
phosphorus fertilizers, in the
synthesis of vitamins and
chlorophyll, • affects the intensity
of redox reactions
• the edges of the leaves acquire an orange,
red or pink shade
• Plant growth is inhibited, leaves are
deformed and die prematurely.
• nitrates accumulate and nitrogen metabolism
is disturbed - the content of ascorbic acid
decreases. • violations of the phosphorus
metabolism of plants are observed.
soybeans, grain and
leguminous crops,
clover, perennial
grasses
To activate the process of iron up take by the plant, a biochemical adaptation of the primary
metabolism is necessary, which requires primarily changes in energy consumption in the form of
macroergic compounds, which are represented in the cell by such basic forms as nicotinamate
(NADadenine) dinucleotide phosphate and adenosine triphosphate. In the course of the
development of any organism, the most important role in providing cells with these components
belongs to mitochondria, since for adaptive reactions, the effect of iron deficiency on these qi
organelles is important[8].
A high degree of mitochondrial sensitivity in this aspect can be explained by the high
need for iron to maintain the activity of metalloenzymes, iron-sulfur proteins and cytochromes,
thanks to the work of which protons and electrons, ultimately, are transferred to the oxygen in
the air. Electron carrier proteins include iron-sulfur proteins (Fig. 1), containing fragments of the
(Fe-S)n ferredoxin cluster. In them, iron is tetrahedrally surrounded by sulfur atoms of thiolate
fragments of cysteine. In addition to cubic clusters of the type [4Fe - 4S], larger ones are also
known: [8Fe – 7S] and [Mo-7Fe-8S-X] (in nitrogenase).
Fig. 1. – A fragment of the iron-sulfur protein structure (Cys is a cytein residue).
Iron is necessary for the synthesis of cytochromes, pyridoxine and other iron-sulfur
proteins, components of the reaction centers of the chloroplast photosystem, cytochrome
oxidase, catalase, peroxidase and other enzymes that play key roles in the main physiological
processes – photosynthesis, respiration, nitrogen fixation and metabolism.
Iron has a special function – indispensable participation in the biosynthesis of chlorophyll.
Therefore, any reason that limits the availability of iron for plants leads to serious diseases, in
particular to chlorosis. When photosynthesis and respiration are impaired and weakened as a
result of the insufficient formation of organic substances from which the plant's body is built,
95https://ucj.org.ua
O. K. Trunova UCJ № 12 / Vol. 88
Manganese is necessary for normal photo
synthesis, participates in the reduction of
CO2, plays a role in maintaining the structure
of chloroplasts. In the absence of manganese,
chlorophyll quickly breaks down in the light.
Manganese activates more than 35 enzymes
involved in various reactions, including nitro
gen metabolism. Owing to this, it is difficult for
plants experiencing a lack of manganese to use
nitrates as a source of nitrogen nutrition. In ad
dition, manganese participates in the synthesis
of vitamin C, other vitamins and sugars, regu
lates the water regime, increases resistance to
adverse factors, affects fruiting and promotes
the acceleration of fruit development.
The lack of manganese greatly affects the in
tensity of photosynthesis in plants. For exam
ple, in oats with a lack of manganese, the inten
sity of photosynthesis drops by about 2 times.
Manganese takes an active part in the release of
oxygen during photosynthesis and water split
ting. Also, in the absence of manganese, chloro
phyll is quickly destroyed in the light. Violation
of the photosynthesis system leads to a sharp
decrease in the carbohydrate content of the
plant, especially in the root part, so the lack of
manganese is a key factor in the slowing down
of the growth of the root system in plants.
Signs of manganese deficiency in plants
most often appear on carbonate soils, on cher
nozems rich in humus, and on soils with a soil
solution pH close to neutral. The highest con
centration of manganese is observed in acidic
soils, where pH is below 6.5. This feature is ex
plained by the fact that with a decrease in pH
by 1.0, the content of mobile manganese in the
soil increases by a factor of 10, i.e. liming reduc
es the content of mobile manganese in the soil,
and the use of acidic fertilizers, on the cont
rary, contributes to its increase. Manganese
deficiency is exacerbated at low temperatures
and high humidity, so winter and perennial
crops are sensitive to its deficiency in spring.
The introduction of sulfur, superphosphates
(substances that acidify the soil) into the soil
increases the content of available manganese.
The lack of manganese in the soil is especially
acutely felt by cereals, in particular oats, as well
as corn, legumes, beets, potatoes, rapeseed,
peas, green crops (dill, parsley, spinach, onion,
horseradish) apple, cherry, raspberry, grapes
[9]. An external sign of manganese deficiency
is leaf spot and necrosis.
Zinc has a great influence on oxidation-re
duction processes, the rate of which is signifi
cantly reduced when it is lacking. Zinc defi
ciency leads to disruption of hydrocarbon con
version processes. It has been established that
with a lack of zinc in the leaves and roots of to
matoes, citrus fruits and other crops, phenol
ic compounds, phytosterols or lecithins accu
mulate, and the starch content decreases. The
importance of zinc for plant growth is closely
related to its participation in nitrogen metabo
lism. Zinc deficiency leads to a significant ac
cumulation of soluble nitrogen compounds –
amines and amino acids, which disrupts pro
tein synthesis. Many studies have confirmed
that the protein content of plants decreases
with zinc deficiency.
Zinc is part of various enzymes: carbonic an
hydrase, triose phosphate dehydrogenase, per
oxidase, oxidase, polyphenol oxidase, etc. The
importance of zinc for plant growth is closely
related to its participation in nitrogen metabo
lism. Zinc deficiency leads to significant ac
cumulation of soluble nitrogen compounds –
amines and amino acids, which disrupts pro
tein synthesis. Many studies have confirmed
that the protein content of plants decreases
96 ISSN 2708-129X. Укр. хім. журн., 2022
THE ROLE OF CHELATE COORDINATION COMPOUNDS OF BIOGENIC METALS IN THE VITAL ACTIVITY OF PLANTS.INORGANIC CHEMISTRY
with a lack of zinc. Under the influence of zinc,
the synthesis of sucrose, starch, the total con
tent of carbohydrates and protein substances
increase. The use of zinc fertilizers increases
the content of ascorbic acid, dry matter and
chlorophyll. Zinc fertilizers increase drought,
heat and cold resistance of plants [10]. Zn2+
ions form complexes with ligands with donor
O and N atoms. Zinc is part of the active center
of many important enzymes, mainly catalyzing
reactions of hydrolysis of peptides, collagen,
phospholipids, etc. Zinc activates carbonichy
drase enzyme (Fig. 2), which is responsible
for the hydration of CO2 in biofluids and the
transfer of H+ ions to СО3
2-, which regulates
one of the most important buffer systems of
the body. Zinc-containing enzymes form of
«zinc fingers» wonderful shape. This happens
because DNA fragments form repetitive do
mains, which «fold» near zinc ions and cha-
racteristic folds – «fingers» appear. The "fingers"
include fragments of the type (Cys)2(His)2,
(Cys)3(His), (Cys)4 or thiolate cluster complex
es with bridging cysteine residues.
a
b
Fig. 2 – Carbonichydrase (a) and a fragment of xanthineoxidase (b).
5
a
b
Fig. 2 – Carbonichydrase (a) and a fragment of xanthineoxidase (b).
Zinc is part of various enzymes: carbonic anhydrase, triose phosphate dehydrogenase,
peroxidase, oxidase, polyphenol oxidase, etc. The importance of zinc for plant growth is closely
related to its participation in nitrogen metabolism. Zinc deficiency leads to significant
accumulation of soluble nitrogen compounds – amines and amino acids, which disrupts protein
synthesis. Many studies have confirmed that the protein content of plants decreases with a lack
of zinc. Under the influence of zinc, the synthesis of sucrose, starch, the total content of
carbohydrates and protein substances increase. The use of zinc fertilizers increases the content of
ascorbic acid, dry matter and chlorophyll. Zinc fertilizers increase drought, heat and cold
resistance of plants [10]. Zn2+ ions form complexes with ligands with donor O and N atoms. Zinc
is part of the active center of many important enzymes, mainly catalyzing reactions of hydrolysis
of peptides, collagen, phospholipids, etc. Zinc activates carbonichydrase enzyme (Fig. 2), which
is responsible for the hydration of CO2 in biofluids and the transfer of H+ ions to СО32-, which
regulates one of the most important buffer systems of the body. Zinc-containing enzymes form
of «zinc fingers» wonderful shape. This happens because DNA fragments form repetitive
domains, which «fold» near zinc ions and characteristic folds – «fingers» appear. The "fingers"
include fragments of the type (Cys)2(His)2, (Cys)3(His), (Cys)4 or thiolate cluster complexes with
bridging cysteine residues.
All cultivated plants in relation to zinc are divided into 3 groups: very sensitive (corn,
flax, hops, grapes, fruits); moderately sensitive (soy, haricot bean, fodder legumes, peas, sugar
beets, sunflower, clover, onions, potatoes, cabbage, cucumbers, berries); slightly sensitive (oats,
wheat, barley, rye, carrots, rice, alfalfa).
Zinc deficiency has the strongest effect on the formation of seeds than on the
development of vegetative organs. Symptoms of zinc deficiency are widely found in various fruit
crops (apple, cherry, Japanese plum, walnut, pecan, apricot, avocado, lemon, grape). Citrus crops
especially suffer from the lack of zinc. With zinc deficiency, chlorotic spots appear on the leaves
of plants, which become pale green, and in some plants they are almost white. In apple, pear, and
walnut trees, zinc deficiency develops the so-called rosette disease, which is expressed in the
formation of small leaves at the ends of branches, which are arranged in the form of a rosette
[11]. With zinc starvation, few fruit buds are laid. The grain yield drops sharply. Among field
crops, zinc deficiency most often manifests itself in corn in the form of a white sprout or a white
tip. An indicator of zinc starvation in legumes (haricot bean, soybeans) is the presence of
chlorosis on leaves, sometimes asymmetric development of the leaf blade. The lack of zinc for
5
a
b
Fig. 2 – Carbonichydrase (a) and a fragment of xanthineoxidase (b).
Zinc is part of various enzymes: carbonic anhydrase, triose phosphate dehydrogenase,
peroxidase, oxidase, polyphenol oxidase, etc. The importance of zinc for plant growth is closely
related to its participation in nitrogen metabolism. Zinc deficiency leads to significant
accumulation of soluble nitrogen compounds – amines and amino acids, which disrupts protein
synthesis. Many studies have confirmed that the protein content of plants decreases with a lack
of zinc. Under the influence of zinc, the synthesis of sucrose, starch, the total content of
carbohydrates and protein substances increase. The use of zinc fertilizers increases the content of
ascorbic acid, dry matter and chlorophyll. Zinc fertilizers increase drought, heat and cold
resistance of plants [10]. Zn2+ ions form complexes with ligands with donor O and N atoms. Zinc
is part of the active center of many important enzymes, mainly catalyzing reactions of hydrolysis
of peptides, collagen, phospholipids, etc. Zinc activates carbonichydrase enzyme (Fig. 2), which
is responsible for the hydration of CO2 in biofluids and the transfer of H+ ions to СО32-, which
regulates one of the most important buffer systems of the body. Zinc-containing enzymes form
of «zinc fingers» wonderful shape. This happens because DNA fragments form repetitive
domains, which «fold» near zinc ions and characteristic folds – «fingers» appear. The "fingers"
include fragments of the type (Cys)2(His)2, (Cys)3(His), (Cys)4 or thiolate cluster complexes with
bridging cysteine residues.
All cultivated plants in relation to zinc are divided into 3 groups: very sensitive (corn,
flax, hops, grapes, fruits); moderately sensitive (soy, haricot bean, fodder legumes, peas, sugar
beets, sunflower, clover, onions, potatoes, cabbage, cucumbers, berries); slightly sensitive (oats,
wheat, barley, rye, carrots, rice, alfalfa).
Zinc deficiency has the strongest effect on the formation of seeds than on the
development of vegetative organs. Symptoms of zinc deficiency are widely found in various fruit
crops (apple, cherry, Japanese plum, walnut, pecan, apricot, avocado, lemon, grape). Citrus crops
especially suffer from the lack of zinc. With zinc deficiency, chlorotic spots appear on the leaves
of plants, which become pale green, and in some plants they are almost white. In apple, pear, and
walnut trees, zinc deficiency develops the so-called rosette disease, which is expressed in the
formation of small leaves at the ends of branches, which are arranged in the form of a rosette
[11]. With zinc starvation, few fruit buds are laid. The grain yield drops sharply. Among field
crops, zinc deficiency most often manifests itself in corn in the form of a white sprout or a white
tip. An indicator of zinc starvation in legumes (haricot bean, soybeans) is the presence of
chlorosis on leaves, sometimes asymmetric development of the leaf blade. The lack of zinc for
All cultivated plants in relation to zinc are
divided into 3 groups: very sensitive (corn,
flax, hops, grapes, fruits); moderately sensitive
(soy, haricot bean, fodder legumes, peas, su
gar beets, sunflower, clover, onions, potatoes,
cabbage, cucumbers, berries); slightly sensitive
(oats, wheat, barley, rye, carrots, rice, alfalfa).
Zinc deficiency has the strongest effect on
the formation of seeds than on the develop
ment of vegetative organs. Symptoms of zinc
deficiency are widely found in various fruit
crops (apple, cherry, Japanese plum, walnut,
pecan, apricot, avocado, lemon, grape). Citrus
crops especially suffer from the lack of zinc.
With zinc deficiency, chlorotic spots appear on
the leaves of plants, which become pale green,
and in some plants they are almost white. In
apple, pear, and walnut trees, zinc deficiency
develops the so-called rosette disease, which is
expressed in the formation of small leaves at
97https://ucj.org.ua
O. K. Trunova UCJ № 12 / Vol. 88
the ends of branches, which are arranged in
the form of a rosette [11]. With zinc starvation,
few fruit buds are laid. The grain yield drops
sharply. Among field crops, zinc deficiency
most often manifests itself in corn in the form
of a white sprout or a white tip. An indicator of
zinc starvation in legumes (haricot bean, soy
beans) is the presence of chlorosis on leaves,
sometimes asymmetric development of the
leaf blade. The lack of zinc for plants is most
often observed on sandy and sub-sandy soils
with a low zinc content, as well as on carbonate
and old plowed soils.
In plants, cobalt affects the accumulation
of nitrogenous substances and carbohydrates,
increases the intensity of respiration and pho
tosynthesis, contributing to the formation
of chlorophyll and reducing its decay in the
dark. Cobalt also increases the overall water
content of plants, especially during droughts,
and is absolutely necessary for the growth of
nodule bacteria and their nitrogen fixation.
In plants, this element is found in ionic form
and in the composition of vitamin B12 (about
4.5%). Plants, like animals, do not synthesize
vitamin B12. It is produced by the bacteria of
nodules of leguminous plants and participates
in the synthesis of methionine. It is part of vi
tamin B12, which is present in the nodules, and
has a noticeable positive effect on the activity
of enzyme hydrogenase, and also increases the
activity of nitrate reductase in the nodules of
legume crops. This trace element affects the ac
cumulation of sugars and fats in plants, has a
beneficial effect on the synthesis of chlorophyll
in plant leaves, reduces its decay in the dark,
increases the intensity of respiration, and the
content of ascorbic acid in plants. As a result of
foliar fertilization with cobalt in plant leaves,
the total content of nucleic acids increases. Co
balt has a noticeable positive effect on the acti
vity of enzyme hydrogenase, and also increases
the activity of nitrate reductase in the tubers of
leguminous crops. Cobalt takes an active part
in oxidation and reduction reactions, stimu
lates the Krebs cycle and has a positive effect
on respiration and energy metabolism, as well
as protein biosynthesis of nucleic acids. Due to
its positive effect on metabolism, protein syn
thesis, assimilation of carbohydrates, etc. It is a
powerful growth stimulator.
As already mentioned, cobalt is part of co
balamin – coenzyme B12 (Fig. 3).
Fig. 3 – Cobalamin fragment near the coordi
nation center.
Cobalamin contains a macrocycle – a corrin
ring connected to a nucleotide and dimethyl
benzimidazole. The cavity in the center of the
corrin ring is occupied by a Co atom with a
coordination number of 5, and the sixth co
ordination position can be occupied by 5-de
oxyadenosine, connected to Co through the
–СН2– group. Due to this, coenzyme B12 is a
rare example of a natural organometallic com
pound. If the sixth coordination position is oc
cupied by any other small ligands, aquacobala
min, hydroxocobalamin, cyanocobalamin are
6
plants is most often observed on sandy and sub-sandy soils with a low zinc content, as well as on
carbonate and old plowed soils.
In plants, cobalt affects the accumulation of nitrogenous substances and carbohydrates,
increases the intensity of respiration and photosynthesis, contributing to the formation of
chlorophyll and reducing its decay in the dark. Cobalt also increases the overall water content of
plants, especially during droughts, and is absolutely necessary for the growth of nodule bacteria
and their nitrogen fixation. In plants, this element is found in ionic form and in the composition
of vitamin B12 (about 4.5%). Plants, like animals, do not synthesize vitamin B12. It is produced
by the bacteria of nodules of leguminous plants and participates in the synthesis of methionine. It
is part of vitamin B12, which is present in the nodules, and has a noticeable positive effect on the
activity of enzyme hydrogenase, and also increases the activity of nitrate reductase in the nodules
of legume crops. This trace element affects the accumulation of sugars and fats in plants, has a
beneficial effect on the synthesis of chlorophyll in plant leaves, reduces its decay in the dark,
increases the intensity of respiration, and the content of ascorbic acid in plants. As a result of
foliar fertilization with cobalt in plant leaves, the total content of nucleic acids increases. Cobalt
has a noticeable positive effect on the activity of enzyme hydrogenase, and also increases the
activity of nitrate reductase in the tubers of leguminous crops. Cobalt takes an active part in
oxidation and reduction reactions, stimulates the Krebs cycle and has a positive effect on
respiration and energy metabolism, as well as protein biosynthesis of nucleic acids. Due to its
positive effect on metabolism, protein synthesis, assimilation of carbohydrates, etc. It is a
powerful growth stimulator.
As already mentioned, cobalt is part of cobalamin - coenzyme B12 (Fig. 3).
Fig. 3 – Cobalamin fragment near the coordination center.
Cobalamin contains a macrocycle – a corrin ring connected to a nucleotide and
dimethylbenzimidazole. The cavity in the center of the corrin ring is occupied by a Co atom with
a coordination number of 5, and the sixth coordination position can be occupied by 5-
deoxyadenosine, connected to Co through the –СН2– group. Due to this, coenzyme B12 is a rare
example of a natural organometallic compound. If the sixth coordination position is occupied by
any other small ligands, aquacobalamin, hydroxocobalamin, cyanocobalamin are formed. In
cobalamin, the CO atom can be in 3 oxidation states: +3, +2, +1, and all of them are low-spin.
The main enzymatic role of cobalamin is related to the exchange transfer of H or CH3 radicals
between bioligands. Other cobalamin enzymes catalyze radical exchange in the cases of
isomerization (mutase) and dehydration (lyase). Radical exchange begins with the weakening of
the Co-C bond, which leads to the formation of low-spin 5-coordinated Co(II) and the CH2R
radical, which is replaced by any other radical. CH3 group transfer reactions are based on the
high nucleophilicity of the Co+1 ion in a square environment. This reaction takes place during the
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THE ROLE OF CHELATE COORDINATION COMPOUNDS OF BIOGENIC METALS IN THE VITAL ACTIVITY OF PLANTS.INORGANIC CHEMISTRY
formed. In cobalamin, the CO atom can be in
3 oxidation states: +3, +2, +1, and all of them
are low-spin. The main enzymatic role of co
balamin is related to the exchange transfer of H
or CH3 radicals between bioligands. Other co
balamin enzymes catalyze radical exchange in
the cases of isomerization (mutase) and dehyd
ration (lyase). Radical exchange begins with
the weakening of the Co-C bond, which leads
to the formation of low-spin 5-coordinated
Co(II) and the CH2R radical, which is replaced
by any other radical. CH3 group transfer re
actions are based on the high nucleophilicity
of the Co+1 ion in a square environment. This
reaction takes place during the biosynthesis of
methionine, as well as for the activity of metha
nogenic bacteria that produce methane.
Cobalt has a positive effect on the forma
tion of nitrogen-fixing nodule bacteria in le
gumes, improves the growth and development
of plants through the interaction of cell hor
mones during auxin metabolism, participates
in redox reactions, photosynthesis (increases
the amount of chlorophyll), synthesis of nu
cleic acids, promotes the intensity of the pas
sage of respiratory processes, the formation
in plants, carbohydrates, fats, sugars, vitamins
(ascorbic acid), activates enzymes (in particu
lar nitrate reductase), accelerates the develop
ment of vegetative organs, promotes flowering,
can accumulate in pollen, forms frost resis
tance, heat resistance (increases the total water
content), increases resistance to stress - factors,
diseases, in cereals ( resistance to lodging), in
creases productivity, improves the quality of
grown products, promotes better absorption
of nitrogen, potassium, phosphorus, magnesi
um from the soil and limits the entry of heavy
metals into the organs of agricultural plants.
Cobalt can move freely from the leaves to
other organs of the plant, which is an impor
tant indicator in foliar feeding [12, 13].
Copper is an essential redox-active transi
tion metal that is involved in many physiologi
cal processes in plants because it can exist in
multiple oxidation states in vivo. Under phy
siological conditions Cu exists as Cu2+ and Cu+.
Cu acts as a structural element in regulatory
proteins and participates in photosynthetic
electron transport, mitochondrial respira
tion, oxidative stress responses, cell wall me
tabolism and hormone signaling. Cu ions act
as cofactors in many enzymes such as Cu/Zn
superoxide dismutase (SOD), cytochrome c
oxidase, amino oxidase, laccase, plastocyanin
and polyphenol oxidase. At the cellular level,
Cu also plays an essential role in signaling of
transcription and protein trafficking machine
ry, oxidative phosphorylation and iron mobili
zation. Thus, plants require Cu as an essential
micronutrient for normal growth and deve
lopment; when this ion is not available plants
develop specific deficiency symptoms, most
of which affect young leaves and reproductive
organs. The redox properties that make Cu an
essential element also contribute to its inhe
rent toxicity. Redox cycling between Cu2+ and
Cu+ can catalyze the production of highly toxic
hydroxyl radicals, with subsequent damage to
DNA, lipids, proteins and other biomolecules.
Thus, at high concentrations, Cu can become
extremely toxic causing symptoms such as
chlorosis and necrosis, stunting, leaf disco
loration and inhibition of root growth. At the
cellular level, toxicity may result from 1) bind
ing to sulfhydryl groups in proteins, thereby
inhibiting enzyme activity or protein function;
2) induction of a deficiency of other essen
tial ions; 3) impaired cell transport processes;
4) oxidative damage [14, 15].
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O. K. Trunova UCJ № 12 / Vol. 88
8
enzyme superoxide dismutase, has been studied in the most detail. Oxygen carrier proteins
include the protein hemocyanin, which is intracellular, which is generally characteristic of Cu-
containing proteins (Fig. 4).
b
Fig. 4 – Fragment of the structure of copper-containing proteins: hemocyanin (a), plastocyanin (b).
In the hemocyanin oligomer, each monomer unit contains 2 copper atoms located very
close together. Deoxyhemocyanin is colorless, but acquires a bright blue color when binding O2.
In deoxyhemocyanin, the Cu(I) atom has a coordination number of 3 and pyramidally
coordinates 3 histidine residues. After the addition of an O2 molecule, 2 bridging bonds are
formed, which connect 2 copper atoms. At the same time, O2 is reduced to О22-. The protein
residues converge significantly, and the Cu atoms have a coordination number of 5, which is
typical only for Cu(II).
Electron carriers are the so-called "blue" copper proteins containing both Cu(I) and
Cu(II), as well as residues of thiolate groups, imidazole, and cysteine. In plastocyanin and azurin,
there is a planar Cu(I) complex with a coordination number of 3. When coordinating the fourth
ligand, which usually contains a donor sulfur atom, the coordination number of Cu(I) increases
to 4 in a tetrahedral environment.
In cytochrome-C-oxidase and N2O-reductase, the center of the enzyme is a
binuclear complex in which 2 Cu atoms are connected through a bidentate cysteine residue, and
each Cu atom coordinates a heterocyclic imidazole nitrogen atom. In one-electron oxidation of
this form, a purple paramagnetic complex is formed, in which the unpaired electrons belong to
both copper atoms. Despite the fact that a number of other macro- and microelements greatly
affect the rate of redox processes, the effect of copper in these reactions is specific, and it cannot
be replaced by any other element. Under the influence of copper, the activity of peroxysylase
increases and the activity of synthetic centers decreases and leads to the accumulation of soluble
carbohydrates, amino acids and other products of the breakdown of complex organic substances.
Copper is a constituent part of a number of the most important oxidizing enzymes – polyphenol
oxidase, ascorbin oxidase, lactase, dehydrogenase, etc. All of these enzymes carry out oxidation
reactions by transferring electrons from the substrate to molecular oxygen, which is an electron
acceptor. In connection with this function, the valence of copper in redox reactions changes from
a divalent to a monovalent state and back.
Almost all copper in leaves is concentrated in chloroplasts mainly in the form of
plastocyanin and is closely related to the processes of photosynthesis: it stabilizes chlorophyll,
protecting it from destruction. Copper is part of copper protein, forming an oxidizing enzyme,
Plants use Cu as a cofactor for a wide range
of proteins involved in several physiological
processes, including photosynthesis, mito
chondrial respiration, carbohydrate metab
olism, formation of phenolics in response to
pathogen attack, superoxide scavenging, cell
wall remodeling, and ethylene perception.
The majority of Cu proteins (~90%) found in
nature function as oxidoreductases. The most
abundant Cu protein in plants is plastocyanin
(which utilizes about 50% of Cu in plastids),
a protein essential for photosynthetic elec
tron transport in chloroplasts that transfers
electrons from the cytochrome b6f complex
to photosystem I (PSI). Cu is part of Complex
IV of the mitochondrial respiratory chain, and
thus is involved in metabolic pathways that
supply energy for cellular processes. Other Cu
proteins are Cu/Zn superoxide dismutase (dis
mutation of superoxide), laccase (cell wall re
modeling), amine oxidase (cell wall and plant
tissue differentiation, wound healing, and re
sponse to pathogens), and polyphenol oxidase
(wounding and pathogen response) [16].
In plant organisms, copper is found mainly
in the form of copper-containing proteins [17,
18]. There are more than 20 enzymes contain
ing copper in the active center, most of which
are oxidases. Their biological role is related to
the processes of hydroxylation, oxidative cata
lysis, and oxygen transfer. The role of copper
in enzyme cytochrome oxidase, which con
trols the reactions of the О2 → Н2О, О2 → Н2О2
type, as well as the disproportionation reaction
О2- → О2- + Оо, which is very important for the
body, and takes place with the participation of
the enzyme superoxide dismutase, has been
studied in the most detail. Oxygen carrier pro
teins include the protein hemocyanin, which is
intracellular, which is generally characteristic
of Cu-containing proteins (Fig. 4).
In the hemocyanin oligomer, each mono
mer unit contains 2 copper atoms located very
close together. Deoxyhemocyanin is colorless,
but acquires a bright blue color when binding
O2. In deoxyhemocyanin, the Cu(I) atom has
a coordination number of 3 and pyramidally
coordinates 3 histidine residues. After the ad
dition of an O2 molecule, 2 bridging bonds are
formed, which connect 2 copper atoms. At the
same time, O2 is reduced to О2
2-. The protein
residues converge significantly, and the Cu
atoms have a coordination number of 5, which
is typical only for Cu(II).
а b
Fig. 4 – Fragment of the structure of copper-containing proteins: hemocyanin (a), plastocyanin (b).
100 ISSN 2708-129X. Укр. хім. журн., 2022
THE ROLE OF CHELATE COORDINATION COMPOUNDS OF BIOGENIC METALS IN THE VITAL ACTIVITY OF PLANTS.INORGANIC CHEMISTRY
Electron carriers are the so-called "blue" cop
per proteins containing both Cu(I) and Cu(II),
as well as residues of thiolate groups, imidazole,
and cysteine. In plastocyanin and azurin, there
is a planar Cu(I) complex with a coordination
number of 3. When coordinating the fourth
ligand, which usually contains a donor sulfur
atom, the coordination number of Cu(I) in
creases to 4 in a tetrahedral environment.
In cytochrome-C-oxidase and N2O-reduc
tase, the center of the enzyme is a binuclear
complex in which 2 Cu atoms are connected
through a bidentate cysteine residue, and each
Cu atom coordinates a heterocyclic imidazole
nitrogen atom. In one-electron oxidation of
this form, a purple paramagnetic complex is
formed, in which the unpaired electrons be
long to both copper atoms. Despite the fact
that a number of other macro- and microele
ments greatly affect the rate of redox processes,
the effect of copper in these reactions is spe
cific, and it cannot be replaced by any other
element. Under the influence of copper, the
activity of peroxysylase increases and the ac
tivity of synthetic centers decreases and leads
to the accumulation of soluble carbohydrates,
amino acids and other products of the break
down of complex organic substances. Copper
is a constituent part of a number of the most
important oxidizing enzymes – polyphenol
oxidase, ascorbin oxidase, lactase, dehydroge
nase, etc. All of these enzymes carry out oxi
dation reactions by transferring electrons from
the substrate to molecular oxygen, which is
an electron acceptor. In connection with this
function, the valence of copper in redox reac
tions changes from a divalent to a monovalent
state and back.
Almost all copper in leaves is concentrated
in chloroplasts mainly in the form of plastocy
anin and is closely related to the processes of
photosynthesis: it stabilizes chlorophyll, pro
tecting it from destruction. Copper is part of
copper protein, forming an oxidizing enzyme,
and promotes the synthesis of iron-contain
ing enzymes in plants. It positively affects the
synthesis of proteins in plants, which ensure
the ability of plant tissues to retain water, as
a result, copper in the form of fertilizer adds
drought and frost resistance to plants and pro
tection against bacterial and fungal diseases.
Copper participates in the process of nitrogen
fixation by plants, increases resistance to lodg
ing. In practice, copper is used in crop produc
tion, especially on poor peat-swamp soils. With
its deficiency, young leaves quickly wither and
dry without visible signs of chlorosis, abnormal
intense shedding is often observed. [19].
When feeding with ammonia nitrogen, the
lack of copper delays the incorporation of ni
trogen into protein, peptones, and peptides
already in the first hours after nitrogen fertili
zation. This indicates a particularly important
role of copper in the application of ammonia
nitrogen. A characteristic feature of the action
of copper is that this trace element increases the
resistance of plants against fungal and bacterial
diseases. Copper reduces grain crops diseases
of various types of smut, increases the resis
tance of plants to brown spot, etc. Symptoms
of plant diseases with a lack of copper in the
soil are manifested for cereals in the whitening
and drying of the tips of the leaf blade. With a
strong lack of copper, the plants begin to bush
intensively, but later earing does not occur, and
the entire stem gradually dries up. Fruit crops
with a lack of copper suffer from the so-called
dry top or exanthema. At the same time, pro
nounced chlorosis develops between the veins
on the leaf blades of plum and apricot trees. In
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O. K. Trunova UCJ № 12 / Vol. 88
tomatoes, when there is a lack of copper, the
growth of shoots slows down, the development
of roots is weak, the appearance of dark blu
ish-green leaves and their twisting, the absence
of flower formation. Copper deficiency nega
tively affects plant reproduction. Pollen grains
are formed in smaller quantities, and for cereals,
an empty ear grain is characteristic. [15, 20].
Thus, summarizing the need and behavior
of Cu in plants, the following conclusions can
be drawn:
1. Cu is mainly complexed with organic
compounds of low molecular weight and with
proteins.
2. Cu is found in compounds that do not
have conducting functions, as well as in en
zymes that have vital functions in plant meta
bolism.
3. Cu plays an important role in several
physiological processes – photosynthesis, res
piration, carbohydrate distribution, reduction
and fixation of N, protein exchange and cell
wall metabolism.
4. Cu affects the water permeability of xy
lem vessels and thus controls water relations.
5. Cu controls the production of DNA and
RNA, and its deficiency significantly inhibits
plant reproduction (reduction of seed produc
tion, pollen sterility).
6. Cu is involved in disease resistance me
chanisms. This resistance of plants to fungal
diseases is likely to be associated with an ade
quate supply of Cu. There is also evidence that
Cu-enriched plants are susceptible to some
diseases. These phenomena may indicate an
indirect effect of Cu on plant disease resistance.
Currently, molybdenum has been put for
ward in one of the first places among other
microelements in terms of its practical impor
tance, since this element turned out to be a very
important factor in solving one of the cardinal
problems of modern agriculture – providing
plants with nitrogen. With a lack of molybde
num, a large amount of nitrates accumulates
in plant tissues and the normal nitrogen me
tabolism is disturbed [21]. Molybdenum is an
essential component in two enzymes that con
vert nitrate into nitrite (a toxic form of nitro
gen) and then into ammonia before it is used to
synthesize amino acids within the plant. It also
needed by symbiotic nitrogen fixing bacteria
in legumes to fix atmospheric nitrogen. Mo is
involved in hydrocarbon exchange, in the ex
change of phosphorus fertilizers, in the synthe
sis of vitamins and chlorophyll, and affects the
intensity of redox reactions. After seed treat
ment with molybdenum, the content of chlo
rophyll, carotene, phosphorus and nitrogen
in the leaves increases. It was established that
molybdenum is part of the enzyme nitrate re
ductase, which restores nitrates in plants. The
activity of this enzyme depends on the level of
supply of plants with molybdenum, as well as
on the forms of nitrogen used for their nutri
tion. With a lack of molybdenum in the nutri
ent medium, the activity of nitrate reductase is
sharply reduced [22, 23].
Molybdenum is able to detect both different
oxidation states (+4, +5, +6) and variable co
ordination numbers (4, 5, 6, 8). Therefore, the
biological action of Mo is diverse. It is the pre
sence of Mo that allows leguminous plants to
assimilate atmospheric nitrogen, in the body
of animals, Mo is part of redox enzymes, in
cluding xanthine oxidase, which is involved in
the exchange of purines and the transfer of O2.
With an excess of Mo in the soil, it accumulates
in the body, which contributes to the activation
of xanthine oxidase (Fig. 5) and the synthesis
of an excessive amount of uric acid.
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THE ROLE OF CHELATE COORDINATION COMPOUNDS OF BIOGENIC METALS IN THE VITAL ACTIVITY OF PLANTS.INORGANIC CHEMISTRY
Fig. 5 – Fragment of xanthine oxidase.
Like most metals required for plant growth,
molybdenum is used by special plant enzymes
to participate in reduction and oxidation re
actions. Molybdenum is an integral part of an
organic pterin complex called molybdenum
cofactor (Moco). The coordination unit of a
Mo-containing enzyme is usually formed from
thiolate ligands (for example, pterin), cysteine
residues and is supplemented with ligands
with donor oxygen atoms: water molecules,
OH- and O2- groups. Moco binds to molybde
num-requiring enzymes (molybdoenzymes)
found in most biological systems, including
plants. When plants are grown under molyb
denum deficiency, a number of varied phe
notypes develop, which hinder plant growth.
Most of these phenotypes are associated with
reduced activity of molybdoenzymes. These
enzymes include primary nitrogen assimila
tion enzymes, such as nitrate reductase (NR),
and nitrogen-fixing enzyme nitrogenase found
in bacteroids of legume nodules. Other mo
lybdoenzymes have also been identified in
plants, including xanthine dehydrogenase/oxi
dase involved in purine catabolism and urei
de biosynthesis in legumes, aldehyde oxidase
(AO), which is involved in ABA biosynthesis,
and sulfite oxidase, which can convert sulfite
to sulfate, an important step in the catabo
lism of sulfur-containing amino acids [22–24].
The value of molybdenum in the life of
plants is quite diverse. It activates atmospheric
nitrogen binding processes of nodule bacteria,
promotes the synthesis and exchange of pro
tein substances in plants. The most sensitive
to molybdenum deficiency are such crops as
soybeans, grain legumes, clover, and perennial
grasses. Plant's need for molybdenum fertili
zers usually increases on acidic soils with a pH
below 5.2. The physiological role of molybde
num is related to the fixation of atmospheric
nitrogen, the reduction of nitrate nitrogen in
plants, participation in redox processes, carbo
hydrate metabolism, and the synthesis of chlo
rophyll and vitamins. Nitrate reductase with
the participation of molybdenum catalyzes the
reduction of nitrates and nitrites, and nitrite
reductase also with the participation of mo
lybdenum reduces nitrates to ammonia. This
explains the positive effect of molybdenum on
increasing the protein content of plants. Under
the influence of molybdenum, the content of
carbohydrates, carotene and ascorbic acid also
increases in plants, and the content of protein
substances increases. Under the influence of
molybdenum, the content of chlorophyll in
plants increases, and the intensity of photosyn
thesis increases.
10
with molybdenum, as well as on the forms of nitrogen used for their nutrition. With a lack of
molybdenum in the nutrient medium, the activity of nitrate reductase is sharply reduced [22, 23].
Molybdenum is able to detect both different oxidation states (+4, +5, +6) and variable
coordination numbers (4, 5, 6, 8). Therefore, the biological action of Mo is diverse. It is the
presence of Mo that allows leguminous plants to assimilate atmospheric nitrogen, in the body of
animals, Mo is part of redox enzymes, including xanthine oxidase, which is involved in the
exchange of purines and the transfer of O2. With an excess of Mo in the soil, it accumulates in
the body, which contributes to the activation of xanthine oxidase (Fig. 5) and the synthesis of an
excessive amount of uric acid.
Fig. 5 – Fragment of xanthine oxidase.
Like most metals required for plant growth, molybdenum is used by special plant enzymes to
participate in reduction and oxidation reactions. Molybdenum is an integral part of an organic
pterin complex called molybdenum cofactor (Moco). The coordination unit of a Mo-containing
enzyme is usually formed from thiolate ligands (for example, pterin), cysteine residues and is
supplemented with ligands with donor oxygen atoms: water molecules, OH- and O2- groups.
Moco binds to molybdenum-requiring enzymes (molybdoenzymes) found in most biological
systems, including plants. When plants are grown under molybdenum deficiency, a number of
varied phenotypes develop, which hinder plant growth. Most of these phenotypes are associated
with reduced activity of molybdoenzymes. These enzymes include primary nitrogen assimilation
enzymes, such as nitrate reductase (NR), and nitrogen-fixing enzyme nitrogenase found in
bacteroids of legume nodules. Other molybdoenzymes have also been identified in plants,
including xanthine dehydrogenase/oxidase involved in purine catabolism and ureide biosynthesis
in legumes, aldehyde oxidase (AO), which is involved in ABA biosynthesis, and sulfite oxidase,
which can convert sulfite to sulfate, an important step in the catabolism of sulfur-containing
amino acids [22–24].
The value of molybdenum in the life of plants is quite diverse. It activates atmospheric
nitrogen binding processes of nodule bacteria, promotes the synthesis and exchange of protein
substances in plants. The most sensitive to molybdenum deficiency are such crops as soybeans,
grain legumes, clover, and perennial grasses. Plant's need for molybdenum fertilizers usually
increases on acidic soils with a pH below 5.2. The physiological role of molybdenum is related
to the fixation of atmospheric nitrogen, the reduction of nitrate nitrogen in plants, participation in
redox processes, carbohydrate metabolism, and the synthesis of chlorophyll and vitamins. Nitrate
reductase with the participation of molybdenum catalyzes the reduction of nitrates and nitrites,
and nitrite reductase also with the participation of molybdenum reduces nitrates to ammonia.
This explains the positive effect of molybdenum on increasing the protein content of plants.
Under the influence of molybdenum, the content of carbohydrates, carotene and ascorbic acid
also increases in plants, and the content of protein substances increases. Under the influence of
molybdenum, the content of chlorophyll in plants increases, and the intensity of photosynthesis
increases.
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O. K. Trunova UCJ № 12 / Vol. 88
The availability of molybdenum for plant
growth strongly depends on soil pH, concen
tration of adsorbing oxides (e.g., Fe oxides),
degree of drainage of water and organic com
pounds contained in soil colloids. In alkaline
soils, molybdenum becomes more soluble
and available to plants mainly in anion form.
On the contrary, in acidic soils (pH<5.5), the
availability of molybdenum decreases, as the
adsorption of anions by soil oxides increases
[25]. When plants are grown under the con
ditions of molybdenum deficiency, a number
of different phenotypes develop, which inhibit
plant growth. Most of these phenotypes are as
sociated with the reduced activity of molybdo
enzymes.
The lack of molybdenum in plants is mani
fested in the bright green color of the leaves,
while the leaves themselves become narrow,
their edges curl inward and gradually die, a dot
appears, the leaf veins remain light green. The
lack of molybdenum manifests itself, first of all,
by the appearance of the yellow-green color of
leaves, which is a consequence of the weaken
ing of atmospheric nitrogen fixation, the stems
and petioles of plants become reddish-brown.
Nickel belongs to conditionally essential ele
ments. Nickel is a component of some plant
enzymes, especially urease, which metabo
lizes urea nitrogen into useable ammonia in
the plant. Without nickel, toxic levels of urea
can accumulate in tissues; forming necrotic
legions on leaf tips. Currently, there is a suf
ficiently large number of scientific works in
which the beneficial effects of Ni compounds
on plant growth have been proven [26]. The ele
ment Ni is considered an indispensable trace
element for plants because it acts as an activa
tor of the urease enzyme. Recent studies have
shown that Ni can activate the glyoxalase I
isoform, which performs an important step in
the degradation of methylglyoxal (MG), a po
tent cytotoxic compound naturally produced
by cellular metabolism. Reduced glutathione
(GSH) is consumed and regenerated in the de
toxification process of MG produced during
stress (stress-induced production). [26, 27]
investigated the role of Ni in the interrelation
between the MG cycle and GSH homeostasis
and suggested that Ni may play a key role in
the metabolism of plant antioxidants, espe
cially in stressful situations. Some researchers
demonstrated the effect of Ni stimulation on
the nitrification and mineralization of nitroge
nous compounds [28], and in [29] it was estab
lished that microorganisms that metabolize H2
and urea are highly sensitive to Ni nutrition.
It was shown in [30] that water-soluble forms
of nickel compounds in small concentrations
are easily absorbed by plant roots, which has a
positive effect on their development.
In [31] it was found that Ni binds to ani
onic organic complexes in xylem exudates.
Although the transport and storage of Ni ap
pears to be metabolically controlled, this metal
is mobile in plants and is likely to accumulate
simultaneously in leaves and seeds. It should
be noted that Ni is easily and quickly taken up
by plants from soils, and until a certain con
centration of Ni in plant tissue is reached, ad
sorption is positively correlates with soil Ni
concentrations.
Nickel is found in soil as a free ion and in
complexes with other metal ions (such as Fe).
In soils, Ni exists in various states of oxidation,
but the predominant and more stable form is
Ni2+, which exists in a wide range of pH and re
dox potentials. The biological effects of Ni are
very related to its forms, however, regardless
of the chemical form of Ni introduced into the
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THE ROLE OF CHELATE COORDINATION COMPOUNDS OF BIOGENIC METALS IN THE VITAL ACTIVITY OF PLANTS.INORGANIC CHEMISTRY
soil, Ni was found in plants only in the form
of neutral and negative complexes. Ni cations
are included in the structure of many enzymes,
including glyoxalases, ureases, methyl-CoM
reductases, superoxide dismutases, peptide
deformalylases, and some hydrogenases [27,
32, 33]. It plays an important role in ureolysis,
methane biogenesis, acetogenesis, hydrogen
metabolism, as well as in the maintenance of
the cellular redox state, tolerance to stress and
protection and optimal use of nitrogen [34–
36]. Deficiency of nickel ions in plants causes
accumulation of urea and necrotic lesions in
plant leaves.
At excessive concentrations of nickel in
plants, its phytotoxic effect is manifested –
photosynthesis and transpiration are inhibited
in plant tissues. At the same time, the develop
ment of roots and metabolism lag behind. The
most common symptom of Ni toxicity is Fe-in
duced chlorosis, in which the foliar Fe level
is reduced. Another manifestation of nickel
toxicity is the reduction of plant growth and
photosynthesis caused by induced oxidative
stress, inhibition of nitrogen metabolism and
enzymatic activity. Thus, nickel salts play a
significant role in the growth and development
of plants. The absorption of nickel by plants is
achieved either by active transport or by pas
sive diffusion, depending on the plant species,
soil pH, the form of nickel compounds, their
concentration, and the availability of other
metals. Solubilized nickel compounds can be
transported by various cationic transport sys
tems, such as Fe2+, Mg2+, Cu2+, Zn2+ in the form
of chelates with citric acid, histidine, and nico
tiamine, as well as with various proteins, such
as permeases, metallothionein, metallochape
rones [37–39].
Nickel for plants is an important ultra-mi
croelement that takes part in biological nit
rogen fixation. The particular importance of
the element lies in the increase of resistance to
negative manifestations of the environment,
which significantly affects the increase in pro
ductivity. Nickel is responsible for the hydro
lysis of urea in the plant body (conversion of
urea into ammonium (NH4+), as it is an indis
pensable component of enzyme urease. Nickel
has fungicidal properties due to the fact that
it directly affects pathogenic organisms or ac
tivates the protective properties of the crop.
In addition, Ni is the main nutrient for nitro
gen-fixing bacteria.
USAGE OF MICRO ELEMENTS IN CROP
GROWING. In total, about 75 chemical ele
ments of Mendeleev's periodic system were
found in plant cells, which are part of enzymes,
hormones, vitamins and other biologically
active compounds. Each of the elements per
forms its specific function and ensures the
normal growth and development of crops.
Microelements («metals of life») are necessary
for the construction of enzyme systems (bio
catalysts) for all plants, and it is impossible to
replace them with other macro- or meso-ele
ments. For normal life, crops need more than
30 trace elements in sufficient quantities, in
cluding both metals (Cu, Zn, Co, Mo, Mn, etc.)
and non-metals (I, Si, Se, Br, F, etc.), which are
part of various chemical compounds contained
in the soil (Table 2.).
When there is a lack of available forms of
boron, manganese, copper, molybdenum, and
in certain conditions also cobalt, zinc, iodine,
vanadium and other microelements in the soil,
specific diseases of crops are observed, they
give a low and inferior yield. In this case, the
use of appropriate microfertilizers eliminates
plant diseases and significantly increases the
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O. K. Trunova UCJ № 12 / Vol. 88
yield and quality of crop production. Under
the action of microelements, the sugar content
of many plants increases, the content of starch
or protein, vitamins and fats increases. The
resistance of plants to drought, high and low
temperatures also increases, their susceptibili
ty to pests and diseases decreases. The value of
trace elements goes far beyond crop produc
tion, as many animal and human diseases are
often associated with a lack of trace elements.
Table 2.
Physiological need of agricultural crops for trace elements [40].
Crop/trace element B Cu Fe Mn Zn Mo
Corn ** ** ** ** *** *
Sorghum * ** *** *** *** *
Soy * * *** *** ** ***
Wheat * *** * *** * *
Barley * *** * ** * *
Pea * * * *** * **
Sunflower *** ** * ** ** *
Sugar beet *** ** ** *** ** **
Rape *** * * *** * ***
Flax ** *** * * *** *
Tomatoes ** ** ** ** ** *
Cucumbers * ** * *** * *
Onion *** ** *** ** ** ***
White-headed cabbage *** ** * *** ** ***
Cauliflower *** ** * ** * ***
Carrot *** *** * *** * *
Potato ** * * ** ** *
Grape *** ** *** *** *** *
Apple tree *** ** *** *** *** *
*** - key microelement; ** - vital microelement; * - an important microelement
A deficiency in the soil of certain trace
elements can be detected by the appearance
of specific signs in the appearance of plants.
However, in the practice of agriculture, one has
often to meet with a less acute shortage of trace
elements, when clear external signs are not
observed, but the growth and development of
plants are suppressed and they give low yields.
The need for the use of microfertilizers can be
de`termined based on the results of a chemi
cal soil analysis for the content of plant-avai
lable forms of microelements. With the grea
test accuracy, the need to apply microfertili
zers in specific soil and climatic conditions can
be judged by the results of field experiments.
A higher efficiency of using microfertilizers, as
a rule, is observed when plants are well sup
plied with the main nutrients - nitrogen, phos
phorus and potassium. At the same time, the
introduction of the necessary trace elements
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THE ROLE OF CHELATE COORDINATION COMPOUNDS OF BIOGENIC METALS IN THE VITAL ACTIVITY OF PLANTS.INORGANIC CHEMISTRY
significantly increases the effect of nitrogen,
phosphorus and potassium fertilizers. When
microelements are introduced, a better use of
nutrients from the soil and mineral fertilizers
by plants is ensured.
But only a small part of trace elements in
the soil solution is in a mobile form, easily ab
sorbed by plants. Therefore, when filling their
lack, the form of compounds (degree of availa
bility for the plant organism) in which they
will be in the soil should be taken into account.
Most trace elements are part of enzymes and
act as active catalysts that accelerate important
biochemical reactions in plants. Insignificant
amounts of microelements in combined ac
tion strengthen their catalytic functions and
greatly influence the course of life processes
in crops. In addition, they affect the orienta
tion of biochemical processes. For example,
copper protects chlorophyll from destruction
and contributes to an almost twofold increase
in the doses of nitrogen and phosphorus. Man
ganese regulates the ratio of divalent and triva
lent iron in plant cells. Boron and manganese
have a positive effect on the recovery of crops
after freezing, they contribute to the flow of
photosynthesis in them. Microelements are of
decisive importance in activating the regene
rative functions of tissues and resistance of
the plant organism to various diseases. They
are indispensable in increasing the immunity
of plants and reducing their susceptibility to
parasitic diseases. Only the complete supply of
plants with all the necessary trace elements al
lows crops to fully use energy, water and basic
nutrients (nitrogen, phosphorus, potassium),
and as a result, to form higher yields.
Microfertilizers are able to eliminate plant
diseases that arose as a result of an incorrect
ratio of macroelements (N, P, K) in their nu
trition. When one or more microelements are
insufficiently supplied to plant cells, there is a
decrease in the rate and coherence of the phy
siological processes responsible for the de
velopment of the plant organism. As a result,
plants are not able to realize their genetic po
tential, the level and quality of their yield are
significantly reduced. Therefore, along with
the main elements of mineral nutrition, which
contain macro- and mesoelements, it is neces
sary to take care of the introduction of complex
fertilizers, which contain all the microelements
necessary for crops.
The metabolic action and role of each mic
roelement in plants can be characterized in re
lation to some basic processes, such as:
1. Absorption and transport inside the plant
2. Enzymatic processes
3. Concentrations and forms of occurrence
4. Deficiency and toxicity
5. Ionic competition and interaction
Chemical balance in living organisms is
the main condition for their proper growth
and development. The interaction of chemi
cal elements also has a similar importance to
deficiency and toxicity in plant physiology. In
teractions between chemical elements can be
both antagonistic and synergistic, and their
unbalanced reactions can cause real chemical
stress in plants. Antagonism occurs when the
combined physiological effect of two or more
elements is less than the sum of their inde
pendent effects, and synergism occurs when
the combined effect of these elements is great
er. These interactions can also relate to the
ability of one element to inhibit or stimulate
the absorption of other elements in plants. All
these reactions are quite variable and can oc
cur inside cells, inside membrane surfaces, and
also in plant roots.
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Below are examples of «interaction»of mac
ro- and microelements in plants [2, 3].
Zinc-phosphorus – a high level of availa
ble P causes a deficiency of zinc, which may
be associated with the formation of insolu
ble Zn3(PO4)2 in the soil. P-Zn antagonism in
roots affects zinc translocation.
Zinc-nitrogen – high levels of nitrogen cause
a deficiency of zinc due to increased growth
rate with a limiting supply of Zn; retention of
Zn in the roots due to the formation of a stable
N-Zn protein complex.
Iron-phosphorus – an excessive amount of
P and an increase in the P/Fe ratio inactivates
iron. This effect is probably due to the forma
tion of a slightly soluble Fe-phosphate preci
pitate, and the plant is able to absorb and re
tain Fe in a soluble, mobile form, the amount
of which decreases with an increase in the con
centration of P in tissues. Similar phenomena
occur with copper-phosphorus imbalance in
plants.
Molybdenum-sulfur – the absorption of Mo
by plants reduces the S content by direct com
petition between two equivalent anions of the
same size; another explanation suggests that
the inhibition of Mo utilization in the plant
occurs at low Mo levels.
Zinc-magnesium – аn increase in the pH of
the soil, after the use of MgCO3, causes the in
teraction of Zn and Mg inside the plant and in
the soil.
Zinc-iron – the metabolic functioning of
Fe in plants is closely related to the balanced
supply of Zn, but with excessive addition of Zn
there is a noticeable decrease in the concentra
tion of Fe in plants.
Iron-manganese – Fe and Mn are intercon
nected in their metabolic functions, the effec
tiveness of one determines the proportional
presence of the other. An excess of Mn reduces
the availability of Fe, because Mn prevents the
transport of Fe from roots to shoots.
Iron-molybdenum – two effects of Mo and
Fe are proposed - a beneficial and a harmful
one. With an excess of Mo, there is a deficien
cy of Fe due to the formation of Fe-molybdate,
which leads to a decrease in the content of Fe
in the solid body (roots). On the other hand, at
an equivalent level of these elements, Mo in
creases the absorption of Fe.
Copper-iron – іn several crops and mainly
citrus fruits, Fe-chlorosis occurs due to a high
concentration of Cu in the nutrient solution
Copper-molybdenum – the antagonism of
Cu and Mo in plants is observed when Cu in
terferes with the role of Mo in the enzymatic
reduction of NO3.
As mentioned above, plants can easily use
trace elements only in a biologically active wa
ter-soluble form (mobile form of a microele
ment), and the immobile form can be used by
the plant after complex biochemical processes
involving soil humic acids. In the middle of the
20th century, trace elements in crop produc
tion were mainly used in the form of inorganic
salts of trace elements, which were mainly in
troduced into the soil in significant quantities.
Adding them to the soil contributes to their
better assimilation and hence to a more effec
tive effect on the yield of plants. Preparations
of this type have a low cost, which attracts the
attention of farmers. However, the use of salts
of trace elements is appropriate only on acidic
and slightly acidic soils. Salts of inorganic acids
are poorly soluble, so they are difficult for
plants to assimilate. Their excess can cause a
toxic reaction and soil salinization. The twen
ty-first century is the period of the use of more
effective preparations of microelements in the
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THE ROLE OF CHELATE COORDINATION COMPOUNDS OF BIOGENIC METALS IN THE VITAL ACTIVITY OF PLANTS.INORGANIC CHEMISTRY
form of chelated microfertilizers. They are
more effective due to the availability of trace
elements for plants, and act as dual action
drugs.
MICROELEMENTS IN CHELATED FORM.
Currently, particular attention is given to the
role of microelements in living organisms as
complexing agents, since most biochemical ob
jects in plants are in the form of coordination
compounds [41–43]. Living organisms prefer
compounds of those elements that are capable
of forming sufficiently strong but at the same
time labile bonds. These bonds should be easi
ly subjected to both homolytic and heterolytic
rupture as well as cyclization. Such organogens
are microelements. The microelements must
be introduced into the body in an active form,
capable of being transported and absorbed.
From this point of view, chelate complexes of
biometals are promising [2, 44].
In recent decades, the development of nano
technology has reached its height. Of particu
lar interest to researchers are nanosystems of
a given composition with predicted properties.
When used in chemistry, medicine, biotech
nology, the size of nano particles or nano-sys
tems is of great importance because it depends
on the permeability, activity, solubility and
toxicity of nanoparticles [45, 46].
The biocoordination compounds of metals
as medical and biological agents form the ba
sis of modern socially and technologically sig
nificant innovative developments. Combining
metal ions with an organic compound enables
the production of supramolecular associates,
which are inherently close to the endogenous
coordination compounds that exist in the liv
ing organism and in general in biosystems.
They are less toxic than their constituents and
usually have a wide range of biological acti
vity. The attention of the world scientific com
munity to this area is caused by its intensive
development, as well as the achievements of
biocoordination, bioorganic, medical chemist
ry. More and more new complexing ions and
ligands are involved in the orbit of biochemical
research. disorders of plants.
The theory and practice of the experimen
tal chemistry of biologically active substances
are related to the development of fundamen
tal principles for the creation of effective drugs
based on the structure-activity dependence,
which, in turn, is associated with the develop
ment of theoretical methods, as well as the ac
cumulation of information on the relationship
of molecular structure with biological activity.
The effectiveness of the influence of the micro
elements on any living organism quantitatively
and directly depends on the form in which the
microelements is.
The twenty-first century is a period of use
of more effective chelate-based microelements
They are more effective due to the availabili
ty of microelements for living organisms and
act as dual action drugs. Chelating compounds
(chelates) are coordination compounds of
metal (microelements ) with a chelating agent
(chelant, ligand) of a cyclic nature. Complex
ons are the most promising chelating agents.
Complexones belong to complex amino
carboxylic (aminophosphonic) acids, which
contain several functional groups: carboxylic
(–C (O) O–), phosphonic (PO3H2), and amino
(NH-) groups. Therefore, thanks to chemical
interaction, it is possible to obtain metal-con
taining compounds in which metal ions will
bind to the ligand with the help of electron-do
nating atoms (oxygen and nitrogen) with the
formation of heterocyclic rings (metal-che
late cycles).
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Among the multifunctional complex-form
ing compounds, polyaminocarboxylate, phos
phonic, and aminophosphonic complexones
are the most promising from a biological point
of view for creating microfertilizers [3, 48–50].
In table 3, the most common chelating agents
that are currently used to create microfertili
zers and in fig. 6 structural formulas of some
complexions are shown.
Almost all microelements form fairly stable
complexes with the given ligands, while the
form of the complexes strongly depends on the
pH of the solution or soil. The most favorable
conditions for the formation of complexes are
non-alkaline environments (pH ~ 5.5–6.5).
In terms of biochemical structure and
chemical purity, chelated complexes of micro
elements are very similar to organometallic
compounds synthesized in plant cells (Fig. 7,
a, b). Therefore, upon entering a living cell,
these substances will be perceived by them not
as alien elements, but as «their own», which
will ensure their biogenic compatibility and
accordingly, high absorption [51–54].
16
Fig. 6 - Structural formulas of some complexones.
Almost all microelements form fairly stable complexes with the given ligands, while the
form of the complexes strongly depends on the pH of the solution or soil. The most favorable
conditions for the formation of complexes are non-alkaline environments (pH ~ 5.5–6.5).
In terms of biochemical structure and chemical purity, chelated complexes of
microelements are very similar to organometallic compounds synthesized in plant cells (Fig. 7, a,
b). Therefore, upon entering a living cell, these substances will be perceived by them not as alien
elements, but as «their own», which will ensure their biogenic compatibility and accordingly,
high absorption [51–54].
Table 3.
Chelating agents.
Abbreviation The name of the complexones Formula
EDTA Ethylenediaminetetraacetic acid C10H16O8N2
DTPA Diethylenetriaminepentaacetic acid C14H23O10N3
CDTA Cyclohexane Tetraacetic acid C14H22O8N2
EDDHA Ethylenediamine-Q-hydroxyphenylacetic acid C18H20O6N2
HEDTA Hydroxyethylenediaminetriacetic acid C10H18O7N2
EDDS Ethylenediaminedisuccinic acid C10H16 O8N2
NTA Nitrilotriacetic acid C6H9O6N
EGTA Ethyleneglyco-bis(2-aminoethylether)tetraacetic acid C14H24O10N2
HEDP Hydroxyethylenediphosphonic acid C2H8O7P2
NTP Nitrilotrimethylphosphonic acid C3H12NO9P3
EDТP Ethylenediaminetetraphosphonic acid
CIT Citric acid C6H8O7
OX Oxalic acid C2H2O4
Fig. 6 - Structural formulas of some complexones.
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THE ROLE OF CHELATE COORDINATION COMPOUNDS OF BIOGENIC METALS IN THE VITAL ACTIVITY OF PLANTS.INORGANIC CHEMISTRY
Table 3.
Chelating agents.
Abbreviation The name of the complexones Formula
EDTA Ethylenediaminetetraacetic acid C10H16O8N2
DTPA Diethylenetriaminepentaacetic acid C14H23O10N3
CDTA Cyclohexane Tetraacetic acid C14H22O8N2
EDDHA Ethylenediamine-Q-hydroxyphenylacetic acid C18H20O6N2
HEDTA Hydroxyethylenediaminetriacetic acid C10H18O7N2
EDDS Ethylenediaminedisuccinic acid C10H16 O8N2
NTA Nitrilotriacetic acid C6H9O6N
EGTA Ethyleneglyco-bis(2-aminoethylether)tetraacetic acid C14H24O10N2
HEDP Hydroxyethylenediphosphonic acid C2H8O7P2
NTP Nitrilotrimethylphosphonic acid C3H12NO9P3
EDТP Ethylenediaminetetraphosphonic acid
CIT Citric acid C6H8O7
OX Oxalic acid C2H2O4
17
a b
Fig. 7 – General structure (a) and a fragment of molecular structure (b) of transition metal complexes
with EDDS [51].
An organic molecule seems to capture metal in a «claw», and when in contact with a plant, the
cell membrane recognizes this complex as a substance related to biological structures, and
further the metal ion is absorbed by the plant, and the chelant breaks down into simpler
substances (Fig. 8) [3, 49, 53].
Fig. 8 – The structure of the chelate of a microelement and the action of a chelated microfertilizer on
plant leaf rotation.
The complexonates of microelements have a number of valuable properties: they are
non-toxic, dissolve well enough in water, have high stability in a wide pH range, and are not
destroyed by microorganisms [3, 4, 6]. It is in complexonates that the microelement is
transferred into a mobile, biologically active form. The chelate serves to protect the metal ion,
prevents it from reacting with the environment and keeps it in a highly soluble form that can be
absorbed by plants, even at a pH that naturally leads to their deposition.
The difference between the two forms of microelements (inorganic salts and chelates)is
as follows:
• trace elements in the form of inorganic salts work satisfactorily only in acidic soils (pH up to
6). In soils close to neutral, their effectiveness decreases tenfold. In neutral, weakly alkaline and
carbonate soils, inorganic salts cannot retain microelements in a water-soluble form available to
plants and their efficiency approaches zero, i.e. they change to poorly soluble forms (hydroxides,
carbonates) and become unavailable to plants;
• complex ions are stable in all types of soils, and there are no restrictions on soil pH for them;
• microelement complexes are much more effective than ordinary salts, and accordingly their
consumption is less. This form of microelements can be used, figuratively speaking, in
homeopathic doses, that is, as a prophylactic without even taking into account the composition of
the soil and without causing any harm to nature [53].
Among the listed chelants, the most stable complexes are formed by
polyaminopolycarboxylic acids (EDDS, EDTA, DTPA, CDTA, EDDHA), which have a high
specificity for the iron ion Fe3+ at a certain pH. When increasing the pH, the order of stability of
17
a b
Fig. 7 – General structure (a) and a fragment of molecular structure (b) of transition metal complexes
with EDDS [51].
An organic molecule seems to capture metal in a «claw», and when in contact with a plant, the
cell membrane recognizes this complex as a substance related to biological structures, and
further the metal ion is absorbed by the plant, and the chelant breaks down into simpler
substances (Fig. 8) [3, 49, 53].
Fig. 8 – The structure of the chelate of a microelement and the action of a chelated microfertilizer on
plant leaf rotation.
The complexonates of microelements have a number of valuable properties: they are
non-toxic, dissolve well enough in water, have high stability in a wide pH range, and are not
destroyed by microorganisms [3, 4, 6]. It is in complexonates that the microelement is
transferred into a mobile, biologically active form. The chelate serves to protect the metal ion,
prevents it from reacting with the environment and keeps it in a highly soluble form that can be
absorbed by plants, even at a pH that naturally leads to their deposition.
The difference between the two forms of microelements (inorganic salts and chelates)is
as follows:
• trace elements in the form of inorganic salts work satisfactorily only in acidic soils (pH up to
6). In soils close to neutral, their effectiveness decreases tenfold. In neutral, weakly alkaline and
carbonate soils, inorganic salts cannot retain microelements in a water-soluble form available to
plants and their efficiency approaches zero, i.e. they change to poorly soluble forms (hydroxides,
carbonates) and become unavailable to plants;
• complex ions are stable in all types of soils, and there are no restrictions on soil pH for them;
• microelement complexes are much more effective than ordinary salts, and accordingly their
consumption is less. This form of microelements can be used, figuratively speaking, in
homeopathic doses, that is, as a prophylactic without even taking into account the composition of
the soil and without causing any harm to nature [53].
Among the listed chelants, the most stable complexes are formed by
polyaminopolycarboxylic acids (EDDS, EDTA, DTPA, CDTA, EDDHA), which have a high
specificity for the iron ion Fe3+ at a certain pH. When increasing the pH, the order of stability of
An organic molecule seems to capture metal
in a «claw», and when in contact with a plant,
the cell membrane recognizes this complex as a
substance related to biological structures, and
further the metal ion is absorbed by the plant,
and the chelant breaks down into simpler sub
stances (Fig. 8) [3, 49, 53].
a b
Fig. 7 – General structure (a) and a fragment of molecular structure (b) of transition metal complexes
with EDDS [51].
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O. K. Trunova UCJ № 12 / Vol. 88
Fig. 8 – The structure of the chelate of a microelement and the action of a chelated microfertilizer on
plant leaf rotation.
17
a b
Fig. 7 – General structure (a) and a fragment of molecular structure (b) of transition metal complexes
with EDDS [51].
An organic molecule seems to capture metal in a «claw», and when in contact with a plant, the
cell membrane recognizes this complex as a substance related to biological structures, and
further the metal ion is absorbed by the plant, and the chelant breaks down into simpler
substances (Fig. 8) [3, 49, 53].
Fig. 8 – The structure of the chelate of a microelement and the action of a chelated microfertilizer on
plant leaf rotation.
The complexonates of microelements have a number of valuable properties: they are
non-toxic, dissolve well enough in water, have high stability in a wide pH range, and are not
destroyed by microorganisms [3, 4, 6]. It is in complexonates that the microelement is
transferred into a mobile, biologically active form. The chelate serves to protect the metal ion,
prevents it from reacting with the environment and keeps it in a highly soluble form that can be
absorbed by plants, even at a pH that naturally leads to their deposition.
The difference between the two forms of microelements (inorganic salts and chelates)is
as follows:
• trace elements in the form of inorganic salts work satisfactorily only in acidic soils (pH up to
6). In soils close to neutral, their effectiveness decreases tenfold. In neutral, weakly alkaline and
carbonate soils, inorganic salts cannot retain microelements in a water-soluble form available to
plants and their efficiency approaches zero, i.e. they change to poorly soluble forms (hydroxides,
carbonates) and become unavailable to plants;
• complex ions are stable in all types of soils, and there are no restrictions on soil pH for them;
• microelement complexes are much more effective than ordinary salts, and accordingly their
consumption is less. This form of microelements can be used, figuratively speaking, in
homeopathic doses, that is, as a prophylactic without even taking into account the composition of
the soil and without causing any harm to nature [53].
Among the listed chelants, the most stable complexes are formed by
polyaminopolycarboxylic acids (EDDS, EDTA, DTPA, CDTA, EDDHA), which have a high
specificity for the iron ion Fe3+ at a certain pH. When increasing the pH, the order of stability of
The complexonates of microelements have
a number of valuable properties: they are
non-toxic, dissolve well enough in water, have
high stability in a wide pH range, and are not
destroyed by microorganisms [3, 4, 6]. It is in
complexonates that the microelement is trans
ferred into a mobile, biologically active form.
The chelate serves to protect the metal ion,
prevents it from reacting with the environment
and keeps it in a highly soluble form that can
be absorbed by plants, even at a pH that natu
rally leads to their deposition.
The difference between the two forms of
microelements (inorganic salts and chelates)is
as follows:
• trace elements in the form of inorganic
salts work satisfactorily only in acidic soils (pH
up to 6). In soils close to neutral, their effec
tiveness decreases tenfold. In neutral, weakly
alkaline and carbonate soils, inorganic salts
cannot retain microelements in a water-solu
ble form available to plants and their efficien
cy approaches zero, i.e. they change to poorly
soluble forms (hydroxides, carbonates) and be
come unavailable to plants;
• complex ions are stable in all types of soils,
and there are no restrictions on soil pH for
them;
• microelement complexes are much more
effective than ordinary salts, and accordingly
their consumption is less. This form of micro
elements can be used, figuratively speaking, in
homeopathic doses, that is, as a prophylactic
without even taking into account the composi
tion of the soil and without causing any harm
to nature [53].
Among the listed chelants, the most stable
complexes are formed by polyaminopolycar
boxylic acids (EDDS, EDTA, DTPA, CDTA,
EDDHA), which have a high specificity for the
iron ion Fe3+ at a certain pH. When increas
ing the pH, the order of stability of the com
plexes decreases as follows: EDDHA> DTPA>
CDTA> EDTA> EDDS (Fig. 9) [3]. It should
be noted that EDDHA has a high selectivity
for Fe3+ in a wide pH range (from 4 to 9), but,
unfortunately, this effective chelant forms sta
ble complexes only with iron, and the stability
of complexes with other necessary microele
ments (Mn, Cu, Zn, Co) is significantly low
er [55]. Therefore, in the modern practice of
creating chelated microfertilizers, the EDDHA
complex is used extremely rarely, although it is
allowed by the European Union Directive EU
2003/2003 of October 13, 2003 for the produc
tion of mineral fertilizers.
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THE ROLE OF CHELATE COORDINATION COMPOUNDS OF BIOGENIC METALS IN THE VITAL ACTIVITY OF PLANTS.INORGANIC CHEMISTRY
Fig. 8 – Comparison of Fe-chelate stabilities in soil solution [3].
18
the complexes decreases as follows: EDDHA> DTPA> CDTA> EDTA> EDDS (Fig. 9) [3]. It
should be noted that EDDHA has a high selectivity for Fe3+ in a wide pH range (from 4 to 9),
but, unfortunately, this effective chelant forms stable complexes only with iron, and the stability
of complexes with other necessary microelements (Mn, Cu, Zn, Co) is significantly lower [55].
Therefore, in the modern practice of creating chelated microfertilizers, the EDDHA complex is
used extremely rarely, although it is allowed by the European Union Directive EU 2003/2003 of
October 13, 2003 for the production of mineral fertilizers.
.
Fig. 8 – Comparison of Fe-chelate stabilities in soil solution [3].
There are various factors affecting the stability of metal chelates, which are primarily
related to the nature of metals and the nature of the chelating agent (ligand). The influence of
metal ions on the stability of chelates is manifested as follows: at the same degree of oxidation
for metal ions of the same family (for example, 3d, alkaline earth elements), the stability of
complexes increases with a decrease in the ionic radius. So for Ca(II) complexes lgKst. is higher
than for the corresponding strontium complex. For the same metal, as the ion charge increases,
the stability constant increases (for example, Fe3+ chelates are more stable than Fe2+ in most
cases). And finally, stability depends on the electronegativity of the metal ion and increases as
follows: (eV) Cu (1.9) > Fe (1.8) > Zn (1.6) > Mn (1.5) > Ca (1.0), which makes it possible to
create a stronger covalent bond.
The effect of stabilization of the complex due to the chelating agent depends on the
structure of the ligand (stability increases with the formation of a larger number of metallocycles
between the metal ion and the chelating agent), the affinity of cations to the donor atoms of the
ligand (for example, for a zinc ion, when coordination bonds with donor atoms are formed,
stability changes in the series S> N> O, while for Ca ions there is no significant difference
between these three donors). The stability of the complexes is significantly affected by the steric
effect. When the atoms are too close to each other, energy is wasted due to overlapping electron
There are various factors affecting the sta
bility of metal chelates, which are primarily re
lated to the nature of metals and the nature of
the chelating agent (ligand). The influence of
metal ions on the stability of chelates is mani
fested as follows: at the same degree of oxi
dation for metal ions of the same family (for
example, 3d, alkaline earth elements), the sta
bility of complexes increases with a decrease in
the ionic radius. So for Ca(II) complexes lgKst.
is higher than for the corresponding strontium
complex. For the same metal, as the ion charge
increases, the stability constant increases (for
example, Fe3+ chelates are more stable than
Fe2+ in most cases). And finally, stability de
pends on the electronegativity of the metal ion
and increases as follows: (eV) Cu (1.9) > Fe
(1.8) > Zn (1.6) > Mn (1.5) > Ca (1.0), which
makes it possible to create a stronger covalent
bond.
The effect of stabilization of the complex
due to the chelating agent depends on the
structure of the ligand (stability increases with
the formation of a larger number of metallo
cycles between the metal ion and the chelat
ing agent), the affinity of cations to the donor
atoms of the ligand (for example, for a zinc ion,
when coordination bonds with donor atoms
are formed, stability changes in the series
S> N> O, while for Ca ions there is no signi
113https://ucj.org.ua
O. K. Trunova UCJ № 12 / Vol. 88
ficant difference between these three donors).
The stability of the complexes is significantly
affected by the steric effect. When the atoms are
too close to each other, energy is wasted due to
overlapping electron clouds (Pauli – Born re
pulsion), and this can affect the desired shape
of the molecule (conformation) and reactivity.
And different conformations in space have dif
ferent levels of stability. Complexes that have
a high entropy are more stable, since the most
stable energy state is achieved in them. For
example, for ethylene diamine tetraacetates of
various metals, the entropy (ΔS25С) changes in
the following order: +55 (Cu2+) = +55 (Zn2+)>
+42 (Cu2+)> +41 (Mn2+)> +32 (Mg2+).
Among complexones that contain carboxyl
groups, DTPA is the most optimal, which al
lows the use of complexones (especially iron)
on carbonate soils in a wide pH range (even
at pH above 8), where other complexones are
ineffective. Although, it should be noted that
currently microfertilizers based on EDTA are
produced in the largest quantities, which is
primarily due to its sufficient availability and
relatively low cost.
Currently, the vast majority of chelated mi
crofertilizer preparations are based on com
plexes of two complexones – ethylenediamine
tetraacetic acid and hydroxyethylenediphos
phonic acid. The leadership of these chelants is
due, first of all, to their unique properties (the
possibility of forming complexes with almost
all metals of the Periodic System) in combi
nation with a well-developed theoretical and
experimental base and, of course, economic
feasibility of use. Chelates are produced on the
basis of EDTA, which can be used on soils with
a pH of less than 8, and for each microelement,
stable compounds can be formed only at cer
tain pH values (for example, an iron complex
with EDTA is effective in combating chlorosis
only on moderately acidic soils; in an alkaline
medium it is unstable. It should be noted seve
ral characteristic features of complexes with
EDTA: complexes with molybdenum are rela
tively weak, they decompose in an alkaline en
vironment; Ca and Mg chelates are soluble, but
less stable compared to other trace elements;
no complexes are formed with boron). In ad
dition, chelates with EDTA are decomposed by
soil microorganisms, which leads to the tran
sition of trace elements to an insoluble form.
These drugs exhibit antiviral activity.
Of the complexones containing phosphonic
groups, HEDP is the most promising. On its ba
sis, all individual metal complexonates used in
agriculture, as well as compositions of various
compositions and ratios, can be obtained. In
its structure, it is closest to natural compounds
based on polyphosphates (during its decom
position, chemical compounds are formed that
are easily absorbed by plants). Chelates based
on it can be used on soils with a pH of 4.5–11.
A distinctive feature of this chelating agent is
that, unlike EDTA, it can form stable complex
es with Mo and B. However, it is a very weak
chelating agent for iron, copper, and zinc. In
the nutrient solution or root zone, these ions
are easily replaced by calcium and their effec
tiveness is significantly reduced. HEDP is re
sistant to the action of soil microorganisms.
The conditions of solubility of HEDP complex
es, which are strictly differentiated depending
on the complexing metal, make it possible to
obtain microfertilizers of prolonged action.
The specificity of the interaction of OEDP
with calcium ions allows changing the physi
cochemical and granulometric properties of
various mineral fertilizers. It should be not
ed that the use of HEDP-based chelates in
114 ISSN 2708-129X. Укр. хім. журн., 2022
THE ROLE OF CHELATE COORDINATION COMPOUNDS OF BIOGENIC METALS IN THE VITAL ACTIVITY OF PLANTS.INORGANIC CHEMISTRY
working solutions on very hard natural waters
is unacceptable, however, acidification elimi
nates this drawback. In addition, HEDP pre
vents the formation of poorly soluble salts in
nozzles, pipelines of nutrient systems and is a
growth regulator.
The formation of stable complexes of metals
with HEDP can be explained by the formation
of chelate structures due to the bidentate coor
dination of the ligand by two oxygen atoms of
phosphonic groups to the cation. At the same
time, stable eight-membered cycles are formed,
which can be strengthened by intramolecular
bonds with the participation of water mole
cules, formed in the case of the interaction of
a metal cation with the oxygen atoms of two
phosphate groups at the same time, which can
be strengthened by intramolecular bonds with
the participation of water molecules:
Нydroxyethylidenediphosphonic acid is
close in its structure to natural compounds
based on polyphosphates (its decomposition
produces chemical compounds easily digested
by plants).
Other complexones are also used as chelat
ing agents, for example, ethylenediamine
(2-hydroxy-4-methylphenyl)acetic acid. Che
lates based on it can be used in pH ranges from
3.5 to 11.0. However, the cost of this highly ef
fective agent is quite significant. The issues of
the use of 3-d metal complexes based on eth
ylenediaminedisuccinic acid are covered quite
widely in the literature. These complexes are
very stable (lgKst.~13–18) in a wide pH range
(3–10) and are biologically active, non-toxic
and environmentally friendly compounds [56,
57]. The type of chelating agent strongly affects
the efficiency of the fertilizer and the degree
of assimilation of trace elements by the plant:
chelates based on lignins are absorbed 4 times
better, those based on citrates 6 times better,
and those based on classical aminopolycar
boxylates and/or polyphosphonates (EDTA,
HEDP, DTPA) – in 8–10 times better than tra
ditional inorganic fertilizers [58]. In chelated
microfertilizers based on traditional comple
xones such as EDTA, DTPA, NTA, HEDP, the
active component is only the ion of a biologi
cally active trace element, and the organic part
of the compounds performs only a transport
function – diffuse delivery of trace elements
to plants. In complexes based on EDDS, the
chelant not only delivers the trace element, but
also has a biological activity itself. Upon en
tering to a living organism, the organic part of
ethylene diamine disuccinates under the influ
ence of sunlight or UV radiation breaks down
into essential amino acids (arginine, leucine,
isoleucine, valine, histidine, asparagine, ala
nine), which are present in the living organism
as components of the metabolic chain (Fig. 9,
table 4) [59–61].
Fig. 9 – Chromatogram of photolysis products
of FeІІІEDDS model solutions (C=1·10-3 mol/l) after
irradiation λ=345 nm [60, 61].
19
clouds (Pauli – Born repulsion), and this can affect the desired shape of the molecule
(conformation) and reactivity. And different conformations in space have different levels of
stability. Complexes that have a high entropy are more stable, since the most stable energy state
is achieved in them. For example, for ethylene diamine tetraacetates of various metals, the
entropy (ΔS25С) changes in the following order: +55 (Cu2+) = +55 (Zn2+)> +42 (Cu2+)> +41
(Mn2+)> +32 (Mg2+).
Among complexones that contain carboxyl groups, DTPA is the most optimal, which
allows the use of complexones (especially iron) on carbonate soils in a wide pH range (even at
pH above 8), where other complexones are ineffective. Although, it should be noted that
currently microfertilizers based on EDTA are produced in the largest quantities, which is
primarily due to its sufficient availability and relatively low cost.
Currently, the vast majority of chelated microfertilizer preparations are based on
complexes of two complexones – ethylenediaminetetraacetic acid and
hydroxyethylenediphosphonic acid. The leadership of these chelants is due, first of all, to their
unique properties (the possibility of forming complexes with almost all metals of the Periodic
System) in combination with a well-developed theoretical and experimental base and, of course,
economic feasibility of use. Chelates are produced on the basis of EDTA, which can be used on
soils with a pH of less than 8, and for each microelement, stable compounds can be formed only
at certain pH values (for example, an iron complex with EDTA is effective in combating
chlorosis only on moderately acidic soils; in an alkaline medium it is unstable. It should be noted
several characteristic features of complexes with EDTA: complexes with molybdenum are
relatively weak, they decompose in an alkaline environment; Ca and Mg chelates are soluble, but
less stable compared to other trace elements; no complexes are formed with boron). In addition,
chelates with EDTA are decomposed by soil microorganisms, which leads to the transition of
trace elements to an insoluble form. These drugs exhibit antiviral activity.
Of the complexones containing phosphonic groups, HEDP is the most promising. On its
basis, all individual metal complexonates used in agriculture, as well as compositions of various
compositions and ratios, can be obtained. In its structure, it is closest to natural compounds based
on polyphosphates (during its decomposition, chemical compounds are formed that are easily
absorbed by plants). Chelates based on it can be used on soils with a pH of 4.5–11. A distinctive
feature of this chelating agent is that, unlike EDTA, it can form stable complexes with Mo and
B. However, it is a very weak chelating agent for iron, copper, and zinc. In the nutrient solution
or root zone, these ions are easily replaced by calcium and their effectiveness is significantly
reduced. HEDP is resistant to the action of soil microorganisms. The conditions of solubility of
HEDP complexes, which are strictly differentiated depending on the complexing metal, make it
possible to obtain microfertilizers of prolonged action. The specificity of the interaction of
OEDP with calcium ions allows changing the physicochemical and granulometric properties of
various mineral fertilizers. It should be noted that the use of HEDP-based chelates in working
solutions on very hard natural waters is unacceptable, however, acidification eliminates this
drawback. In addition, HEDP prevents the formation of poorly soluble salts in nozzles, pipelines
of nutrient systems and is a growth regulator.
The formation of stable complexes of metals with HEDP can be explained by the
formation of chelate structures due to the bidentate coordination of the ligand by two oxygen
atoms of phosphonic groups to the cation. At the same time, stable eight-membered cycles are
formed, which can be strengthened by intramolecular bonds with the participation of water
molecules, formed in the case of the interaction of a metal cation with the oxygen atoms of two
phosphate groups at the same time, which can be strengthened by intramolecular bonds with the
participation of water molecules:
20
Нydroxyethylidenediphosphonic acid is close in its structure to natural compounds based on
polyphosphates (its decomposition produces chemical compounds easily digested by plants).
Other complexones are also used as chelating agents, for example, ethylenediamine (2-
hydroxy-4-methylphenyl)acetic acid. Chelates based on it can be used in pH ranges from 3.5 to
11.0. However, the cost of this highly effective agent is quite significant. The issues of the use of
3-d metal complexes based on ethylenediaminedisuccinic acid are covered quite widely in the
literature. These complexes are very stable (lgKst.~13–18) in a wide pH range (3–10) and are
biologically active, non-toxic and environmentally friendly compounds [56, 57]. The type of
chelating agent strongly affects the efficiency of the fertilizer and the degree of assimilation of
trace elements by the plant: chelates based on lignins are absorbed 4 times better, those based on
citrates 6 times better, and those based on classical aminopolycarboxylates and/or
polyphosphonates (EDTA, HEDP, DTPA) – in 8–10 times better than traditional inorganic
fertilizers [58]. In chelated microfertilizers based on traditional complexones such as EDTA,
DTPA, NTA, HEDP, the active component is only the ion of a biologically active trace element,
and the organic part of the compounds performs only a transport function – diffuse delivery of
trace elements to plants. In complexes based on EDDS, the chelant not only delivers the trace
element, but also has a biological activity itself. Upon entering to a living organism, the organic
part of ethylene diamine disuccinates under the influence of sunlight or UV radiation breaks
down into essential amino acids (arginine, leucine, isoleucine, valine, histidine, asparagine,
alanine), which are present in the living organism as components of the metabolic chain (Fig. 9,
table 4) [59–61].
Fig. 9 – Chromatogram of photolysis products of FeІІІEDDS model solutions (C=1·10-3 mol/l) after
irradiation λ=345 nm [60, 61].
Table 4.
Products of the photochemical decomposition of Fe(ІІІ) and Mn(ІІ) complexonates with
ethylenediaminedisuccinic acid.
FеЕDDS МnЕDDS
NН3 – 68% NН3 – 89%
СО2 – 82% СO2 – 68%
– Alanin (Ala) – 0,35%
Arginine (Аrg) – 6,3% Arginine (Arg) – 3,89%
Asparagine (Asp) – 1,9% Asparagine (Asp) – 1,8%
Valine (Val) – 0,72% -
Histidine (His) –13,9% Histidine (His) – 9,8%
Isoleucine (Ile) – 0,76% Isoleucine (Ile) – 0,87%
Leucine (Leu) –1,4% Leucine (Leu) – 2,7%
Glutamine (Gln) – 1,34% –
Phenylalanine (Phe) - 11,3% –
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O. K. Trunova UCJ № 12 / Vol. 88
Table 4.
Products of the photochemical decomposition of Fe(ІІІ) and Mn(ІІ) complexonates with
ethylenediaminedisuccinic acid.
FеЕDDS МnЕDDS
NН3 – 68% NН3 – 89%
СО2 – 82% СO2 – 68%
– Alanin (Ala) – 0,35%
Arginine (Аrg) – 6,3% Arginine (Arg) – 3,89%
Asparagine (Asp) – 1,9% Asparagine (Asp) – 1,8%
Valine (Val) – 0,72% -
Histidine (His) –13,9% Histidine (His) – 9,8%
Isoleucine (Ile) – 0,76% Isoleucine (Ile) – 0,87%
Leucine (Leu) –1,4% Leucine (Leu) – 2,7%
Glutamine (Gln) – 1,34% –
Phenylalanine (Phe) - 11,3% –
Depending on the 3d-metal, a different set
of essential amino acids is formed when the
complexes decompose, which is obviously as
sociated with the different nature of the me
tal and the stability of the complexes. But the
main decomposition products are ammonia
and CO2.
The given data show that compounds, the
cation of which can change the valence state,
undergo photochemical decomposition in
solution. The photodecomposition of com
plexes is accompanied, first of all, by decarbox
ylation processes with release of free CO2, as
well as ammonia. The depth of decomposition
increases with increasing pH and the intensity
of irradiation. Since the final products of the
photolysis of complexonates are natural ami
no acids containing residues characteristic of
the EDDS molecule, it can be assumed that the
photodecomposition is accompanied not only
by the breaking of the bond in the original
EDDS molecule, but also by the recombination
of the emerging intermediate products.
The question of the important role of pho
tochemical redox reactions of iron-containing
chelates (the transition of Fe(III) to Fe(II)) is
discussed in [62]. For the implementation of
metabolic processes in plants, a divalent form
of iron is needed. The key value of Fe(II) is de
termined, on the one hand, by the better solu
bility of its mineral salts compared to Fe(III),
and, on the other hand, by the lower stability
of Fe(II)-chelates, which facilitates the release
of iron from transport forms and its further in
corporation into metabolism. The photoreduc
tion of Fe(III) to Fe(II) occurs under the action
of optical radiation with wavelengths less than
420 nm. Optical radiation with a wavelength
distribution in the range of 350–700 nm is able
to penetrate the green leaf and cause photore
duction of Fe (III) in the nutrient solution. This
process occurs both with direct irradiation of
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THE ROLE OF CHELATE COORDINATION COMPOUNDS OF BIOGENIC METALS IN THE VITAL ACTIVITY OF PLANTS.INORGANIC CHEMISTRY
solutions and with their illumination through
leaves affected by chlorosis. With the exclusion
of the ultraviolet part from the composition of
optical irradiation, the photoreduction of Fe
(III) is suppressed. The stimulating effect of
UV radiation on the reduction of Fe(III) and
the synthesis of chlorophyll in leaves was found
in experiments with soybean plants, in which,
under the influence of UV rays, physiological
effects were enhanced and accompanied by an
increase in the amount of chlorophyll and ca
rotenoids.
The mechanism of photolysis of carboxyl-
containing chelates of iron and other trace ele
ments (Mn, Co) consists in the elimination of
the CO2 molecule and the consequent reduc
tion of the chelate cycle. During photolysis, in
termediate products with metal-carbon bonds
are formed. These products are thermally un
stable and form metal ions as well as ligand ra
dicals. For example, the photodecomposition of
Fe-chelates of citric or tartaric acids is accom
panied by the formation of numerous inter
mediate compounds, and the end products of
decomposition are acetone and carbon dioxide.
During the photodecomposition of EDTA, the
following products have been identified: car
bon dioxide, formaldehyde, ethylenediamine
triacetate, ethylenediaminediacetate ions.
In [61], based on the results of mass spec
trometry of metal complexes with ethylene
diaminediansuccinic acid, it was established
that the decomposition of the compounds is
accompanied by the breaking of the C–N bond
and intramolecular rearrangement along the
labile bonds of the ethylene bridge with the
formation of certain amino acid radicals or
amino acids themselves. (Table 5).
Table 5.
Ratio of the mass to the charge of fragments and their interpretation in the mass spectra
of Fe (III) and Mn(II) complexes with EDDS.
m/z
Fragment Interpretation
EDDS FeEDDS MnEDDS
55 64 – -NH2-CH2-CH2-NH2-
Ethylenediamine /
Ethylenediamine radical
69 69 69 -HC-NH-(CH2)2-NH- Fragment EDDS
– 75 75 -NH-CH-COOH Glycine
86 84 84 -NH-CH-(СООН)-CH2- α- Alanin
96 98 96 -NH-CH(СО-)CH2-СО- Asparagine fragment
101 – – -CH2-CH2-СН(NH)COOH Aminobutyric acid
112 112 112 -CH(COO-)CH-COO- Succinic acid radical
– 121 – HOOC-CH2-CH2-COOH Succinic acid
– 130 – -NH-CH(СООН)-CH2-COOH β-Asparagine
– 149 – HOOC-(CH2)2-CH(COOH)NH2 Glutamic acid
158 – – HOOC-CH2-СН(СООН)NH-(CH2)2- –
296 296 – EDDS
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O. K. Trunova UCJ № 12 / Vol. 88
Compared to the mass spectra of pure EDDS,
a larger set of decay products is observed in the
complexes, because the attachment of a metal
to the complex one weakens the carbon-nitro
gen bond due to the coordination of the cation
of amino groups and increases the mobility of
the asparagine fragment of EDDS. The decom
position products of ethylenediaminesuccinic
acid and its complexes are mainly natural com
pounds, which determines the environmental
safety and biological activity of both EDDS it
self and its complexes with microelements.
The study of the stimulating effect of the
FeEDDS complex compared to the effect of
the natural growth stimulator heteroauxin
(HA) on the growth processes of corn showed
that under the influence of the complex, the
length of the leaf and root increases by ~ 45%,
while heteroauxin increases these indicators
by ~ 38% [61]. In this case, the stimulation by
FeEDDS by more significant than that by NA
precisely on the leaves, which are the surface
part of the plant. Presumably, in this case, the
photodestruction of the complexonate under
the action of natural light is more pronounced.
Under the influence of the FeEDDS com
plex, the content and heterogeneity of free
amino acids (alanine, asparagine, glutamine,
glycine, threonine, serine, tyrosine, etc.) in
plants increases (Table 6). In general, the total
amount of amino acids under the action of the
complexing agent increases sharply, in addi
tion, there is an increase in the heterogeneity
of free amino acids.
Also, a distinction of their qualitative com
position under the conditions of stimulation
from that under the conditions of inhibition is
the absence of an increase in the «non-damag
ing2 osmolyte of the cell, while its significant
accumulation is observed under saline condi
tions. This is due to the fact that this is how the
plant reacts to stressful conditions for it, when
growth processes are inhibited. In addition,
this is explained by the different compartmen
talization of the enzymes for the synthesis and
breakdown of proline located in mitochondria.
Under saline conditions, the proportion of pro
line in mitochondrial membranes decreases
and, therefore, its decomposition cannot occur.
Table 6.
The content of amino acids in the leaves of
corn seedlings.
Amino acid Control Experiment
Alanine 12,20 15,8
Methionine 3,12 0,97
Valin 4,63 1,45
Leucine 6,04 4,53
Isoleucine 5,26 5,34
Proline 8,78 7,35
Threonine – 3,27
Serin – 2,44
γ-Aminobutyric acid 7,39 7,68
Arginine 2,39 3,33
Glutamine 4,06 5,55
Asparagine 30,88 33,77
Glycine 2,49 24,01
Lysine 2,45 2,26
Tyrosine – 1,74
Phenylalanine – 5,43
Histidine – 1,66
Amount, % 0,19 0,39
Based on the results obtained, taking into
account the data of [63, 64], an assumption
was made about the mechanism of action of
FeEDDS complexonate in plants.
118 ISSN 2708-129X. Укр. хім. журн., 2022
THE ROLE OF CHELATE COORDINATION COMPOUNDS OF BIOGENIC METALS IN THE VITAL ACTIVITY OF PLANTS.INORGANIC CHEMISTRY
The tricarboxylic acid cycle (TCAC) is a
key step in the respiration of all cells that use
oxygen, the intersection point of many meta
bolic pathways in the body, an intermediate
step between glycolysis and the electron trans
port chain. In addition to a significant ener
gy role, the cycle also performs a significant
plastic function, that is, it is an important
source of precursor molecules, from which,
in the course of other biochemical transfor
mations, such important compounds for cell
life as amino acids, carbohydrates, fatty acids,
etc. are synthesized. The tricarboxylic acid
cycle includes 8 main stages, including the
oxidation of isocitrate to α-ketoglutarate, the
oxidation of α-ketoglutarate to succinyl-CoA,
the conversion of succinyl-CoA to succinate.
It was shown in [63] that the amino acids his
tidine, proline, arginine, glutamine, and glu
tamate can be converted into α-ketoglutarate
and restore its concentration; isoleucine, va
line, methionine, tryptophan - into succinyl-
CoA, aspartate, phenylalanine and tyrosine
into fumarate; aspartate and aspragine to ox
aloacetate. The amino acids alanine, serine,
threonine, cysteine and glycine can be con
verted into pyruvate, which is necessary for
the tricarboxylic acid cycle (Fig. 10).
Fig. 10 – Scheme of the inclusion of amino acids in the tricarboxylic acid cycle [63].
23
enzymes for the synthesis and breakdown of proline located in mitochondria. Under saline
conditions, the proportion of proline in mitochondrial membranes decreases and, therefore, its
decomposition cannot occur.
Based on the results obtained, taking into account the data of [63, 64], an assumption was
made about the mechanism of action of FeEDDS complexonate in plants.
The tricarboxylic acid cycle (TCAC) is a key step in the respiration of all cells that use oxygen,
the intersection point of many metabolic pathways in the body, an intermediate step between
glycolysis and the electron transport chain. In addition to a significant energy role, the cycle also
performs a significant plastic function, that is, it is an important source of precursor molecules,
from which, in the course of other biochemical transformations, such important compounds for
cell life as amino acids, carbohydrates, fatty acids, etc. are synthesized. The tricarboxylic acid
cycle includes 8 main stages, including the oxidation of isocitrate to α-ketoglutarate, the
oxidation of α-ketoglutarate to succinyl-CoA, the conversion of succinyl-CoA to succinate. It
was shown in [63] that the amino acids histidine, proline, arginine, glutamine, and glutamate can
be converted into α-ketoglutarate and restore its concentration; isoleucine, valine, methionine,
tryptophan - into succinyl-CoA, aspartate, phenylalanine and tyrosine into fumarate; aspartate
and aspragine to oxaloacetate. The amino acids alanine, serine, threonine, cysteine and glycine
can be converted into pyruvate, which is necessary for the tricarboxylic acid cycle (Fig. 10).
Fig. 10 – Scheme of the inclusion of amino acids in the tricarboxylic acid cycle [63].
In plants, during the glyoxylate cycle, acetyl-CoA is converted into succinate, which is
further involved in biosynthetic processes [64].
The increase in the pool of free amino acids in plants under the influence of FeEDDS
occurs due to a significant increase in the content of glutamine – one of the main transport forms
of nitrogen. As is known that glutamine in the plant is formed from -ketoglutarate (Fig. 11).
The FeEDDS complex includes two succinate fragments. Therefore, it can be assumed that these
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In plants, during the glyoxylate cycle, acetyl-
CoA is converted into succinate, which is fur
ther involved in biosynthetic processes [64].
The increase in the pool of free amino acids
in plants under the influence of FeEDDS oc
curs due to a significant increase in the content
of glutamine – one of the main transport forms
of nitrogen. As is known that glutamine in the
plant is formed from α-ketoglutarate (Fig. 11).
The FeEDDS complex includes two succi
nate fragments. Therefore, it can be assumed
that these succinate residues are included in
the tricarboxylic acid cycle, going the path to
α-ketoglutarate and, thus, accelerate the main
substrate- and energy-providing process of the
TCAC.
24
succinate residues are included in the tricarboxylic acid cycle, going the path to -ketoglutarate
and, thus, accelerate the main substrate- and energy-providing process of the TCAC.
Fig. 11 – Formation of glutamine in a plant cell.
It is also possible that metal complexes with EDDS somehow activate the path of tryptophan
synthesis or are directly included in this path, and tryptophan is a precursor of auxin – a plant
growth hormone.
APPLICATION OF COMPLEXONATES OF MICROELEMENTS IN PLANT
BREEDING. The use of chelate microelements based on complexonates is very wide, since they
allow providing plants with the necessary microelements by converting ME into a mobile
biologically active form not only in plants, but also in the soil. Metal complexonates used as
microfertilizers are the most effective form of micronutrients and a means of regulating the
production process of agricultural crops, both during seed treatment before sowing and during
root and foliar top dressing [65]. With their help, you can easily correct nutritional deficiencies
that occur as the plant develops (Fig. 12). Especially valuable is the use of chelates at an early
stage of development, when the root system is not yet well formed. In the flowering stage, the
use of foliar dressings with chelates increases the number of ovaries, and fruit processing
increases their sugar content.
Fig.12 – The need of plants for microelements in various phases of growth.
Chelates are compatible with insecticides and pesticides and when used together reduce plant
stress due to the application of pesticides.
Мicroelements in chelated form, enhance plant immunity and serve as a prophylactic against
fungal and viral diseases.
Fig. 11 – Formation of glutamine in a plant cell.
24
succinate residues are included in the tricarboxylic acid cycle, going the path to -ketoglutarate
and, thus, accelerate the main substrate- and energy-providing process of the TCAC.
Fig. 11 – Formation of glutamine in a plant cell.
It is also possible that metal complexes with EDDS somehow activate the path of tryptophan
synthesis or are directly included in this path, and tryptophan is a precursor of auxin – a plant
growth hormone.
APPLICATION OF COMPLEXONATES OF MICROELEMENTS IN PLANT
BREEDING. The use of chelate microelements based on complexonates is very wide, since they
allow providing plants with the necessary microelements by converting ME into a mobile
biologically active form not only in plants, but also in the soil. Metal complexonates used as
microfertilizers are the most effective form of micronutrients and a means of regulating the
production process of agricultural crops, both during seed treatment before sowing and during
root and foliar top dressing [65]. With their help, you can easily correct nutritional deficiencies
that occur as the plant develops (Fig. 12). Especially valuable is the use of chelates at an early
stage of development, when the root system is not yet well formed. In the flowering stage, the
use of foliar dressings with chelates increases the number of ovaries, and fruit processing
increases their sugar content.
Fig.12 – The need of plants for microelements in various phases of growth.
Chelates are compatible with insecticides and pesticides and when used together reduce plant
stress due to the application of pesticides.
Мicroelements in chelated form, enhance plant immunity and serve as a prophylactic against
fungal and viral diseases.
Fig.12 – The need of plants for microelements in various phases of growth.
120 ISSN 2708-129X. Укр. хім. журн., 2022
THE ROLE OF CHELATE COORDINATION COMPOUNDS OF BIOGENIC METALS IN THE VITAL ACTIVITY OF PLANTS.INORGANIC CHEMISTRY
Fig. 13 – Mechanism of metal (Fe) release from chelating agent [3].
25
In complexonates organic acid significantly increases the solubility of the microelement
ion in solution; transports the microelement ion into the plant organism; protects the
microelement ion from transformations of physical and chemical nature; promotes the rapid
involvement of microelement ion in biochemical processes in the plant organism (Fig.13) [3].
Fig. 13 – Mechanism of metal (Fe) release from chelating agent [3].
The main role of chelates is to keep the metal cations in solution so they can diffuse through the
soil to the roots. This is done through the formation of a chelate "ring" around the metal cation,
which protects the metal from interaction with other inorganic compounds. Upon reaching the
plant root, the metal cation either splits out from the chelate and diffuses into the root membrane,
or the entire metal chelate complex is absorbed into the root and then decomposes, releasing the
metal. Both cases result in the extraction of the metal up the root, and the chelate is returned to
the soil solution for binding other metals.
Applying to the soil and spraying with solutions of complexonates of microelements have
a positive effect on the yield of many crops [66–77]. For example, treatment with manganese,
iron, copper, etc. Complexonates on based EDTA and DTPA, of the seeds of cereal, industrial,
grain crops (buckwheat, oats, barley, rye, flax) lead to a change in the terms of plant vegetation,
accelerates the germination of these crops, and increases their yield. In [77] the effect of chelate
compounds of zinc, copper, manganese and iron with HEDP on the yield of spring rapeseed,
white lupine and oats was studied. For comparison, traditional forms of trace elements were used
– vitriol of the corresponding metals. It was found that the chelated forms of microelements had
an advantage over their salt counterparts, providing a biomass yield of rapeseed pods higher than
the best of the options using sulfate for zinc by 56%, for copper – 38%, for manganese – 42%, as
well as an increase in oat grain by 18%. % when using iron. Also, the individual characteristics
of plants in relation to the studied microelements were revealed. Thus, the treatment of spring
rapeseed with chelates containing zinc and copper contributed to the greater development of
generative organs. In [73], a heterometallic complex of magnesium and germaniumIV based on
HEDP – [Mg(H2O)6]3[Ge6(μ-OH)6(μ-HEDP)6]∙20Н2О – was used for the pre-sowing treatment
of winter wheat seeds. It has been proven that the compound increases the field germination of
wheat by 75%. In addition, intensive growth of ground mass (17 cm) and primary root system
(7.5 cm) was observed in the plants. These indicators are significantly higher compared to the
control and standard – complex fertilizer Novalon.
During clonal micropropagation of the gooseberry cultivar at the stage of rhizogenesis,
the efficiency of modification of media with mineral salts according to Quoirin-Lepoivre (QL)
was shown by replacing iron, which is standardly used in the form of FeSO4·7H2O together with
It is also possible that metal complexes with
EDDS somehow activate the path of trypto
phan synthesis or are directly included in this
path, and tryptophan is a precursor of auxin –
a plant growth hormone.
APPLICATION OF COMPLEXONATES
OF MICROELEMENTS IN PLANT BREED-
ING. The use of chelate microelements based
on complexonates is very wide, since they al
low providing plants with the necessary mic
roelements by converting ME into a mobile
biologically active form not only in plants, but
also in the soil. Metal complexonates used as
microfertilizers are the most effective form
of micronutrients and a means of regulating
the production process of agricultural crops,
both during seed treatment before sowing and
during root and foliar top dressing [65]. With
their help, you can easily correct nutritional
deficiencies that occur as the plant develops
(Fig. 12). Especially valuable is the use of che
lates at an early stage of development, when
the root system is not yet well formed. In the
flowering stage, the use of foliar dressings with
chelates increases the number of ovaries, and
fruit processing increases their sugar content.
Chelates are compatible with insecticides
and pesticides and when used together reduce
plant stress due to the application of pesticides.
Мicroelements in chelated form, enhance
plant immunity and serve as a prophylactic
against fungal and viral diseases.
In complexonates organic acid significant
ly increases the solubility of the microelement
ion in solution; transports the microelement
ion into the plant organism; protects the micro
element ion from transformations of physical
and chemical nature; promotes the rapid in
volvement of microelement ion in biochemical
processes in the plant organism (Fig.13) [3].
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O. K. Trunova UCJ № 12 / Vol. 88
The main role of chelates is to keep the metal
cations in solution so they can diffuse through
the soil to the roots. This is done through the
formation of a chelate "ring" around the metal
cation, which protects the metal from interac
tion with other inorganic compounds. Upon
reaching the plant root, the metal cation either
splits out from the chelate and diffuses into
the root membrane, or the entire metal chelate
complex is absorbed into the root and then de
composes, releasing the metal. Both cases re
sult in the extraction of the metal up the root,
and the chelate is returned to the soil solution
for binding other metals.
Applying to the soil and spraying with solu
tions of complexonates of microelements have
a positive effect on the yield of many crops
[66–77]. For example, treatment with man
ganese, iron, copper, etc. Complexonates on
based EDTA and DTPA, of the seeds of cereal,
industrial, grain crops (buckwheat, oats, bar
ley, rye, flax) lead to a change in the terms of
plant vegetation, accelerates the germination of
these crops, and increases their yield. In [77]
the effect of chelate compounds of zinc, copper,
manganese and iron with HEDP on the yield
of spring rapeseed, white lupine and oats was
studied. For comparison, traditional forms of
trace elements were used – vitriol of the corre
sponding metals. It was found that the chelated
forms of microelements had an advantage over
their salt counterparts, providing a biomass
yield of rapeseed pods higher than the best of
the options using sulfate for zinc by 56%, for
copper – 38%, for manganese – 42%, as well
as an increase in oat grain by 18%. % when us
ing iron. Also, the individual characteristics of
plants in relation to the studied microelements
were revealed. Thus, the treatment of spring
rapeseed with chelates containing zinc and
copper contributed to the greater development
of generative organs. In [73], a heterometallic
complex of magnesium and germaniumIV
based on HEDP – [Mg(H2O)6]3[Ge6(μ-OH)6
(μ-HEDP)6]∙20Н2О – was used for the pre-sow
ing treatment of winter wheat seeds. It has
been proven that the compound increases the
field germination of wheat by 75%. In addition,
intensive growth of ground mass (17 cm) and
primary root system (7.5 cm) was observed in
the plants. These indicators are significantly
higher compared to the control and standard –
complex fertilizer Novalon.
During clonal micropropagation of the
gooseberry cultivar at the stage of rhizogene
sis, the efficiency of modification of media with
mineral salts according to Quoirin-Lepoivre
(QL) was shown by replacing iron, which is
standardly used in the form of FeSO4·7H2O
together with Na2EDTA, with chelated forms
with carboxyl-containing ligands Fe(III)-ED
TA and Fe(III)-DTPA and the organophos
phate complexone Fe(II)-HEDP. On the 45th
and 60th days of subculturing, the distribu
tion in descending order of the impact of che
late iron compounds on the rooting rate of
the studied gooseberry plants was as follows:
Fe(III)-EDTA>Fe(III)-DTPA> Fe(II) -HEDP>
Fe(III)-EDDHA>Fe(III)-HEDP. On the 60th
day of subculturing in the best variants of the
experiment, the rooting rate of gooseberry mi
crocuttings of cultivar Pink-2 was 86.7-100%
compared to 60% in the control variant [74].
The effect of organic (Fe-EDTA and Fe-ED
DHA) and inorganic (FeCl3) iron substanc
es on the rooting of the rootstock GF-677
(Prunus amygdalus×Prunus persica – hybrid
of peach and almond) in vitro was studied.
Full rooting (100 %) was observed in ex
plants nourished with Fe-EDDHA, while less
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THE ROLE OF CHELATE COORDINATION COMPOUNDS OF BIOGENIC METALS IN THE VITAL ACTIVITY OF PLANTS.INORGANIC CHEMISTRY
rooting was found in the absence of iron or in
the presence of FeCl3. On the contrary, no root
formation was observed in explants nourished
with Fe-EDTA, which showed extremely lower
chlorophyll and high iron contents at the end
of the experiment [71].
Complexes of 3d-metals with EDDS are en
vironmentally safe biostimulants and positive
ly affect the yield of plants (apple trees, straw
berries, legumes, cabbage, buckwheat, alfalfa,
etc.) [72, 74–77]. Fe[S,S']-EDDS was evaluated
as an iron-containing fertilizer in growing ca
lendula [78]. It has been shown that FeEDDS
complexes are a suitable source of Fe for the
production of marigolds and, most likely, oth
er horticultural crops. Iron sources (FeEDDS,
FeEDTA, FeDTPA, FeEDDHA, and FeSO4) did
not affect marigold leaf count, plant height, dry
weight, or leaf greenness, and there was no evi
dence of bronze spotting or micronutrient toxi-
city syndrome. At the same time, all the main
indicators of the development of calendula
leaves when using chelate complexes and fer
rous sulfate did not differ much and were suf
ficient for normal growth. However, obtaining
concentrated initial solutions of fertilizers with
non-chelate microfertilizers turned out to be
practically impossible due to the low solubility
of the iron salt. Therefore, APCA complexones
(chelates) are necessary to maintain the solu
bility of this metal. And the best fertilizer to
use are FeEDDS/EDDS chelates.
In [79], it was established that no nega
tive consequences are observed when using
FeEDDS on peat soils to increase the yield of
fruit and vegetable crops. The work [80] com
pared the mobility, leaching and availability of
ionc of zinc when using its various complexo
nates (ZnHEDTA, ZnEDDHSA, ZnEDTA,
Zn(S,S)EDDS) on haricot bean. It was estab
lished that the maximum concentration of zinc
in soil leachate was 65 mg/l for Zn(S,S)EDDS
when 10 mg of Zn was applied per 1 kg of soil.
At the same time, the pH of the calcareous soil
increased significantly over the course of the
experiment.
The effect of presowing treatment of spinach
seeds with compounds containing complexo
nes (EDDS, IDS), as well as their complexo
nates with magnesium and zinc, on the content
of chlorophylls and carotenoids in plant leaves
was studied. The effect of complexons was
studied in combination with the exposure of
seeds to a weak constant magnetic field. An in
crease in the content of pigments, participants
in the process of photosynthesis, was record
ed in spinach plants [81]. In the presence of
50 µmol/L Cu, the addition of edds increased
the growth of shoots and roots and decreased
the relative loss of electrolyte from the root cells
of chrysanthemum (Chrysanthemum coronari-
um L.), which led to an increase in the accumu
lation of copper in plant shoots [82].
The results of studies of the effect of EDDS
and its complexes with boron showed a signifi
cant efficiency of using borate complexes in
comparison with the traditional boron micro
fertilizer H3BO3 as stimulators of soil biologi
cal activity and photosynthetic processes in
order to obtain an optimal yield of table beet
root crops [83]. It has been proven that EDDI
AC has a pronounced antimicrobial effect, and
B-EDDS stimulates the microflora. Treatment
with B-EDDS solution caused an increase in
leaf weight by 19% and in root crops by 37%.
The effect of boron compounds on the germi
nation, biomass, and pigment composition of
seedlings of flax, wheat, and Kalanchoe pin
nate, as well as on the nutrient content of Jeru
salem artichoke tubers, was studied [84]. Seed
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O. K. Trunova UCJ № 12 / Vol. 88
germination in a solution of boroethylenedi
amine disuccinate significantly increased the
level of chlorophyll content of flax seedlings.
Treatment with boric acid and free ligand
EDDS also caused some increase in biological
ly active substances. Apparently, not only bo
ron, but also EDDS is included in the metabol
ic processes of the plant as an additional source
of organic carbon and amine nitrogen. The ob
tained data showed that the EDDS borate com
plex turned out to be a more effective fertilizer
for the plant than boric acid or EDDS alone.
The use of B-EDDS significantly increased the
level of chlorophyll in the leaves and seedlings
of wheat, of sugars and pectin in the leaves of
Kalanchoe, inulin and fructose in Jerusalem
artichoke tubers. Some addition of biologically
active substances was also caused by treatment
with boric acid and a free ligand. Apparently,
not only boron, but also complexone is includ
ed in the metabolic processes of the plant as
an additional source of organic carbon. At the
same time, as part of the complex, both com
ponents of the test preparation are more acces
sible to plants than each separately.
Employees of the V.I. Vernadsky Institute of
General and Inorganic Chemistry of National
Academy of Sciences of Ukraine have worked,
for a number of years to create new chelate
forms of microfertilizers based on complex
es of Mn(II), Fe(III), Co(II), Cu(II), Zn(II)
with EDDS [61, 72, 75, 76 , 85–88]. The effect
of complexonates on increasing the yield of
fodder (rapeseed, clover, sweet clover, lupine,
etc.), technical (alfalfa, buckwheat, corn), veg
etable (beets, tomatoes, cabbage) crops, grapes,
flowers was studied in a field experiment
in different regions of Ukraine. Plants were
treated during the period of budding by fo
liar feeding or pre-sowing treatment of grains
with aqueous solutions of preparations with a
metal concentration of 0.05 wt.%. It has been
established that under the action of complexo
nates, the yield of plants increases (15–50%),
the quality of the fodder mass and grain im
proves (the content of sugar, fiber, fats and pro
teins increases). In grape berries, sugar content
increases by 10-12%, and in leaves – the con
tent of chlorophylls and carotenoids increas
es by 59% and 30%, respectively). The use of
preparations on flowers significantly increases
the number of productive stems: by 22% for
carnations and by 42% for roses. In addition,
for roses, an improvement in the elitism of the
variety was noted – an increase and compac
tion of buds. In addition to growth-stimulating
copper complexes, they exhibit a pronounced
fungicidal effect.
The addition of a second biologically active
ligand (citric, tartaric acids, thiourea) or metal
to ethylenediamine disuccinates made it possi
ble to increase the biological activity of the com
plexes. For example, when grapes were treated
with the heterometallic complex, FeCuEDDS,
increased by 7% compared to FeEDDS with
monometallic iron complexonate. In that case,
the absolute content of chlorophylls and caro
tenoids increased by 79% and 37% for the mo
nometal complex and by 93% and 48% for the
heterometallic complex [87].
On the crops of oats and various herbs
(natural meadow grasses), the heterometallic
complex CuCoEDDS was tested, which in
creased the yield of plants by 23% and 13%
respectively. Also, in plants, the amount of
microelements increases greatly: Cu2+ and
Co2+ (by 38%), crude fat, protein and cellulose
(~ 80%) [61]. When lupine and rapeseed plants
are treated with solutions of the MnZnEDDS
complex, the yield of both crops increases by
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THE ROLE OF CHELATE COORDINATION COMPOUNDS OF BIOGENIC METALS IN THE VITAL ACTIVITY OF PLANTS.INORGANIC CHEMISTRY
20% compared to MnEDDS and ZnEDDS.
The content of protein, crude fat and gluten,
sugars increases in plant grains (Table 7). At
the same time, the efficiency of microelements
contained in complexonates is much higher
(especially in the case of MnZnEDDS) than
when using aqueous solutions of inorganic
salts [88, 89].
Mixed-ligand ethylenediaminedisuccinate
complexes of iron and copper with hydroxy
acids and thiourea (THIO) also increase the
yield and quality of grapes, barley, tomatoes,
and peas compared to their monoligand coun
terparts. At the same time, under the action of
CuEDDSTHIO, the number of pea plants af
fected by root rot decreased by 6.2% [61].
Table 7.
Influence of foliar application of the complexes MnEDDS, ZnEDDS, MnEDDS on the
accumulation of some metabolites in rape straw and grain.
Оption
Crude protein, g/kg Crude fat, g/kg Raw gluten, g/kg Sugar, g/kg
straw grain straw grain straw grain straw grain
control 18,4 169 6,3 353 25,4 109 16,3 35,4
MnSO4 17,7 179 6,2 374 24,7 95 15,5 37,6
ZnSO4 20,4 182 6,6 330 23,8 121 17,2 33,7
MnEDDS 20,0 178 6,6 376 25,7 122 16,9 37,7
ZnEDDS 21,7 175 6,8 342 27,9 128 17,2 38,8
MnZnEDDS 22,6 190 6,8 390 28,6 129 18,0 40,2
It is promising to use 3d-metal complexo
nates for the treatment of carbonate chlorosis
in grapes and fruit and berry crops. The calca
reous chlorosis of plants thrives on carbonate
soils, which contain from 10 to 50% and more
carbonates [80]. In such soils at low pH, the
plants are lacking iron and cannot form chlo
rophyll. However, any soil always contains
enough iron. The reason lies in the alkaline
reaction of the soil, because there is too much
lime, due to which iron is in an insoluble and
hence, in an inaccessible form. Due to the lack
of access to the plant organism, as well as the
partial immobilization of iron already present
in its tissues, a situation of deficiency of iron is
created. In addition, chlorosis can be caused by
the presence of high concentrations of metals
such as Mn, Cu, Zn, Co, Ni or Cd, which can
compete with Fe on the level of absorption by
plants. The external manifestation of the phy
siological changes caused by iron deficiency
is chlorosis of leaves - a change in the color
of leaves due to a decrease in the content of
chlorophyll in them. When photosynthesis
and respiration are impaired and weakened as
a result of the insufficient formation of orga
nic substances from which the plant's body is
built, and the lack of organic reserves, a general
metabolic disorder occurs. Therefore, with an
acute lack of iron, the death of plants inevitably
occurs. To protect against chlorosis caused by
iron deficiency on carbonate soils, preparations
containing iron in the form of complexonates
are used [80–82]. The accepted mechanism for
the treatment of iron chlorosis with iron che
lates involves the enzymatic reduction of Fe3+
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O. K. Trunova UCJ № 12 / Vol. 88
to Fe2+ by the chelate of Fe(III) reductase. The
result of this transformation is the release of
Fe2+, which is absorbed by the roots, forming a
free ligand molecule during the process.
The effectiveness of iron chelate in solving
the problem of chlorosis depends on several
factors. The first is the ability of the organic
compound to efficiently chelate Fe3+ and other
metals present in soils (Ca2+, Mg2+ and Cu2+).
Copper is normally present in soils in low con
centrations, but becomes a major competitor to
Fe3+ due to its ability to be chelated by amino
acids. The second factor is the ability of plant
roots to remove Fe3+ from the chelating agent.
This ability is affected by the stability of Fe3+
and Fe2+ chelates. To predict the reactivity of
iron chelates in plants and their effectiveness as
chlorosis correctors, it is necessary to know the
nature of the complexone and the stability of
their complexes with iron, as well as to take into
account their photochemical activity. In a series
of polyaminocarboxylic complexes, stability
increases in the order: FeNTA→ FeEDDHA→
FeEDDS→ FeEDTA→ FeDTPA. Therefore, the
antichlorosis effect of more stable complexes
is more effective than that of medium-resis
tant chelates, and even more so of phosphonic
complexes, which do not affect the synthesis of
chlorophyll in iron-deficient leaves. Obviously,
when phosphonic Fe-chelates are applied to the
leaf surface, their photochemical inertness pre
vents the formation of biologically active Fe(II)
forms. In turn, the differences in the physiolog
ical action between the photochemically active
groups of moderately and highly stable Fe-che
lates may be due to the unequal period of their
photodecomposition. The best antichlorosis
effect is possessed by iron complexes capable
of intensive but prolonged photochemical de
struction [49, 62, 67, 87].
The use of iron(III) complexes in vineyards
showed that spraying grape plants affected by
carbonate chlorosis and/or affected by freezing
has a positive effect on the content of photo
synthetic pigments in the leaves and increases
the yield of plant berries [49, 61, 87, 90, 91].
Fertilization of chlorotic grape plants with
FeEDTA and FeDTPA compounds not only
increases the concentration of chlorophyll in
leaves, but also reduces the content of organic
acids compared to control plants.
USE OF CHELATE COMPOUNDS OF
MICRO ELEMENTS FOR PURIFICATION
OF PLANTS AND SOIL FROM RADIONUC
LIDES. Among the complex systems of mea
sures aimed at minimizing the entry of radio
nuclides from contaminated soil into the first
link of the food chain – the plant, at present
and probably in the coming decades, the most
effective and economically justified system
should be considered the use of mineral and
organic fertilizers. When used purposefully in
certain forms, quantities, ratios and combina
tions, they can be used to reduce the input of
radioactive substances to agricultural plants by
many fold. After the accident at the Chornobyl
nuclear power plant, the area most contaminat
ed by radionuclides is the Ukrainian Polissia
zone, which belongs to a biogeochemical pro
vince, where soils, plants and, accordingly, fod
der and products of plant and animal husband
ry lack many biogenically important trace ele
ments – iodine, zinc, manganese, cobalt, cop
per, fluorine, lithium, boron and some others.
This is the reason of the wide distribution of
specific plant, animal and human diseases in
this zone, which are known under the general
name of hypomicroelement diseases (various
forms of chlorosis, rosette leaves, small leafi
ness in plants; hypocobaltosis, hypocuperosis,
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THE ROLE OF CHELATE COORDINATION COMPOUNDS OF BIOGENIC METALS IN THE VITAL ACTIVITY OF PLANTS.INORGANIC CHEMISTRY
keratosis, alimentary anemia in animals and
humans) [92, 93]. Liming of acidic soils slows
down the mobility and inhibits the transition
from soil to plants not only of radionuclides,
but also of other elements of mineral nutrition.
But this is especially reflected in the content of
trace elements. In [94] it was shown that under
the influence of three times repeated liming of
sod-podzolic soil at a dose of 2 t/ha with an
interval of 4 years, the content of most of the
listed microelements in oat and lupine plants
decreased by almost half. It is known that some
trace elements, including Zn, Mn, Co, Cu, have
radioprotective properties, and some of them
can affect the entry of radionuclides into plants
and animals. Taking into account the situation
with microelements in the region of Ukraine
most contaminated with radionuclides, as well
as their possible role in anti-radiation protec
tion of living organisms, it is possible to pre
dict their special role in the area affected by
the accident. The radiosensitivity of most types
of plants is quite high, so the damage from
the accumulation of radionuclides by plants
and their subsequent transport through food
chains to animals and humans is a much more
important problem than radiation damage to
plants themselves. Therefore, the protective
role of the factors that block the entry of radio
nuclides into plants becomes a more important
element of anti-radiation protection than the
role of radioprotectors. It is indisputable that
the basis of such blocking should be interac
tions occurring between microelements and
radionuclides.
Various interactions are possible between
trace elements and radionuclides:
• additive, in which the effect of the compo
nents is equal to the total sum of the effects of
each component;
• synergistic, when one of the components
enhances the action of the other, as a result of
which the physiological effect of their mixture
exceeds the sum of the effects;
• antagonistic, in which the effect of the ac
tion is smaller than the action of each of the
components separately and than the total ac
tion [95, 96].
Additivity indicates the absence of inter
action between elements. Antagonistic effect
occurs in cases when one of the elements re
duces the concentration of another or com
petes with it for the places of absorption and
further transport, but is unable to replace it
in physiological processes. A synergistic ef
fect is observed when one of the elements can
partially replace the other in some functions
(there can be no question of a complete re
placement). Synergistic interaction can occur
only in cases where an element is multifunc
tional and can perform some functions to
gether with other elements. On this basis, de
pending on the conditions, which primarily
include such indicators as the degree of radio
nuclide pollution, the composition of radio
nuclides, the granulometric composition of
the soil, its agrochemical properties and some
other indicators, three main strategies can be
applied to reduce the degree of radionuclide
entry into plants:
1. Creation of a competitive situation for the
arrival of radionuclides on the basis of antago
nistic interactions between them and elements
of mineral nutrition;
2. Enhancement of the nutrient supply of ra
dionuclide antagonists to plants, based on the
synergism between individual elements and
3. Binding (complex formation) of radio
nuclides in the soil using elements of mineral
nutrition (Table 8).
127https://ucj.org.ua
O. K. Trunova UCJ № 12 / Vol. 88
Table 8.
Possible interactions between macro- and microelements and Cesium-137 and Stron-
tium-90.
Antagonism Element Synergism
B, Cu, F N B, Cu, Fe, Mo
Al, As, B, Be, Ca, Cd, Cr, F, Fe, Hg, Mn, Mo, Ni, Pb, Sb, Si, Sr P B, Co, Cu, Mn, Mo, Zn
Al, F, Cd, Cs, Hg, Mo, Rb, Se K B, Cu, Li, Mn, Zn
Al, B, Ba, Cd, Co, Cs, Fe, Ns, Pb, Si, Sr Ca Cu, Li, Mn, Zn
Al, B, Ba, Co, Cu, Cr, F, Fe, Mn, Ni, Zn Mg Al, Zn
As, Ba, Fe, Mo, Pb, Se S F, Fe
Ba, Ca, Cd, F, Fe, Mg, Li, Zn Sr Pb
Cu, K, Li, Na Cs Cd, Ni
It can be seen from table 8 that microele
ments such as fluorine, iron, cadmium, lithium
and zinc, and the macroelements – calcium,
barium, magnesium can act as antagonists in
relation to 90Sr. Lead is a synergist. In relation
to 137Cs, microelements - copper and lithium,
and macroelements – potassium and sodium
act as antagonists. Synergists of radiocesium
are cadmium and nickel. The given tabular
data show the second possible relationship
between microelements and radionuclides,
when microelements contribute to the supply
of macroelements to plants, and the latter, act
ing as antagonists of radionuclides, affect the
reduction of their supply to plants.
The creation of a competitive situation be
tween trace elements and radionuclides is
based on the interaction of ions of elements
with chemical properties close enough to com
pete for absorption, transport and metabolism.
At the same time, competition will be more
significant for elements and radionuclides with
similar sizes of ionic radii, charge, geometry of
coordination and electronic configuration. The
selection of antagonists can be carried out not
only within one group of the periodic system,
but also among the elements of other, as a rule,
neighboring groups, among elements of varia
ble valences.
Research on the influence of trace elements
on the uptake of radionuclides (137Cs, 90Sr)
into plants was conducted mainly on contami
nated soils in the northwestern part of Ukraine.
A group of researchers under the leadership of
Academician I.M. Gudkov. made a series of field
experiments in the zone of Ukrainian Polissia
to test the most promising trace elements: zinc,
manganese, cobalt, copper, molybdenum, lithi
um, boron and nickel [94, 97–100]. When se
lecting them, a complex of indicators was taken
into account: physiological role, deficiency in
the environment, possible antagonistic inter
actions with radionuclides, possible synergistic
interactions with macroelements-antagonists
of radionuclides, as well as radioprotective pro
perties. The results of these studies indicate that,
under the influence of trace elements, the accu
mulation coefficients (Kaccum. – the ratio of the
radionuclide content of plants to the content
in the soil) of both radionuclides significantly
128 ISSN 2708-129X. Укр. хім. журн., 2022
THE ROLE OF CHELATE COORDINATION COMPOUNDS OF BIOGENIC METALS IN THE VITAL ACTIVITY OF PLANTS.INORGANIC CHEMISTRY
decreased both in comparison with the control
without fertilizers and against the background
of the main fertilizer (nitrogen-phosphate).
The most effective trace element was zinc, un
der the influence of which the KN in oat and
lupine grains in the version without fertilizers
decreased by 2–2.5 times. Manganese and co
balt were somewhat less effective, copper, lithi
um and boron were even less effective. It should
be noted that the effectiveness of microelements
was the greatest in the variants without fertili
zers and the least against the background of in
creased doses of fertilizers. This is quite natural,
since, firstly, with fertilizers, a certain amount
of the most diverse microelements is always in
troduced into the soil in the form of impurities.
And, secondly, in favorable conditions for the
growth and development of plants, which are
provided by fertilizers, the action of all factors,
both positive and negative, is affected to a less
er extent. When foliar feeding of plants (lupine,
rapeseed, etc.) with aqueous solutions of zinc,
manganese, cobalt, and copper sulfates in plants,
the accumulation of 90Sr in the vegetative mass
(straw) and seeds decreases by 25–40%, and
137Сs that of by 1.5 times [89 , 101–103].
Complexionates of microelements are much
more effective in reducing the accumulation of
radionuclides in plant products compared to
their inorganic salts. Numerous works have
shown that the treatment of various plants
with complexonate solutions helps to reduce
the specific radioactivity of both 137Cs and 90Sr
by several times. For example, the work [104]
presents the results of a three-year study the
foliar fertilization of spring wheat crops of the
Struna Myronivska variety with aqueous solu
tions of zinc, manganese and their chelated
analogues with EDTA in different phases of
plant growth and development for the accu
mulation of some trace elements in grain and
straw. It was established that in the early phases
of plant growth and development (spraying in
the tillering phase), there is an increase in the
concentration of both zinc and manganese at
the time of harvesting in both grain and straw,
but for the most part such growth does not in
crease the yield of either grain or straw. In the
case of foliar fertilization of wheat crops, espe
cially with a zinc solution, the accumulation
of iron, potassium, manganese, copper, zinc,
and especially boron ions by plants from the
soil increases by 1.5–2 times both in grain and
in straw compared to the plants of the control
variant. When feeding plants with a MnEDTA
solution, a similar increase in the coefficients of
accumulation of the specified microelements is
observed. At the same time, the transition of
137Cs from the soil to grain decreases by 30–
35%. The highest effect of reducing the levels
of contamination of wheat grain with radioce
sium is observed when feeding plants with a
solution of zinc complexonate in the first half
of the growing season – in the phases of tiller
ing and stooling.
In [105] presents long-term studies on de
termining the accumulation coefficients of
137Cs and 90Sr in the soil and grass of alpine pas
tures in Switzerland. The long-term behavior
of radionuclides was quantified using the ef
fective half-life, which combines all processes
that cause a decrease in activity in a given en
vironment, such as leaching, fixation, erosion
and radioactive decay. The results showed that
90Sr is more transferred from alpine soil to grass
than 137Cs. This is explained by stronger fixation
of Cs in soils. At the same time, the lower the
concentration of calcium in the soil, the high
er the absorption of 90Sr by grass. This is a very
important fact, since it is traditionally believed
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O. K. Trunova UCJ № 12 / Vol. 88
that radio-Sr, accumulating together with calci
um in the skeleton, poses a threat only to blood
cells. But it is well known that calcium is the
main mineral component of plant cell mem
branes and accumulates in increased amounts
in the nuclear envelopes of all types of cells.
Therefore, the high absorption of 90Sr by plants
contributes to the purification of soils from ra
dionuclide pollution, which is an integral part
of phytoremediation. A similar conclusion can
be drawn regarding radio-cesium.
Thus, some microelements can block the
transfer of radionuclides both from the soil to
plants and from plants (forage) to the body of
animals, thus reducing their accumulation in
crop and livestock products. Microelements can
influence certain aspects of metabolism in both
plants and animals, the activity of metal-con
taining enzymes, permeability of membranes.
An intensive study of the effect of chelated
microelements on reducing the accumulation
of long-lived radionuclides 137Cs and 90Sr is be
ing conducted at the Zhytomyr National Agro
ecological University (from 2020, Polis Natio
nal University) under the leadership of Ph.D of
Agricultural Sciences V.M. Bidenko [106–112].
Chelated microfertilizers based on mono- and
heterometallic complexonates with EDDS for
field experiments were provided by a group of
scientists of the Institute of General and Inor
ganic Chemistry named after V.I. Vernadsky
National Academy of Sciences of Ukraine. The
effectiveness of microelement complexonates
(Zn, Co, Mn, Cu) was determined under the
conditions of field experiments on sod-podzo
lic soils of the Zhytomyr region on various ag
ricultural plants (wheat, rye, oats, corn, lupine,
rapeseed, clover, etc.). The results of experi
ments show that foliar feeding of lupine, vetch,
clover, etc. plants with microelement complex
onates helps to reduce the content of Cs-137
and Sr-90 in the green mass of the studied
crops. For example, the 137Cs activity of lu
pine green mass in the control was 671 Bq/kg,
in the variants of using Mn and Zn sulfates, the
137Cs content was equal to ~ 440 Bq/kg, and
in the areas where mono- and heterometallic
complexes (ZnEDDS, MnEDDS, MnZnEDDS)
were used, the 137Cs content was only ~350 and
260 Bq/kg, respectively. That is, microelement
complexonates contributed to a decrease in the
specific activity of Cs-137 by more than 50%
(Fig. 14, a). Both microelements showed a high
radio-blocking effect. Thus, zinc in the form of
a salt solution reduced the accumulation of ra
dio-cesium by more than 1.5 times), and in the
form of ZnEDDS – by 2.1 times. The results of
the action of trace elements on the accumula
tion of 90Sr in plants were distinguished, first
of all, by high coefficients of accumulation of
the radionuclide (Kacum.=4.33). The influence
of microelements in the form of salts on the
accumulation of 90Sr in lupine plants was man
ifested to a somewhat lesser extent compared
to monometallic complexonates. The most ef
fective data, as in the experiments with 137Cs,
turned out to be in the version with the hete
rometallic complex MnZnEDDS – the accu
mulation of radio-strontium in the vegetative
mass of lupine decreased by 34% (Fig. 14, b).
It should be noted that microelements used
as microfertilizers contributed to the activation
of metabolic processes in plants through phyto
hormones, enzymes, vitamins, improvement of
metabolic processes in chlorophylls, contribut
ing to the accumulation of metabolites in crops.
In addition, under the influence of complexo
nates, an increase in some microelements was
observed in plants compared to the control:
copper, zinc, iron and manganese [113].
130 ISSN 2708-129X. Укр. хім. журн., 2022
THE ROLE OF CHELATE COORDINATION COMPOUNDS OF BIOGENIC METALS IN THE VITAL ACTIVITY OF PLANTS.INORGANIC CHEMISTRY
Fig. 14 – Influence of microelements and their complexonates on the accumulation
of 137Cs and 90Sr in the lupine vegetative mass.
32
(ZnEDDS, MnEDDS, MnZnEDDS) were used, the 137Cs content was only ~350 and 260 Bq/kg,
respectively. That is, microelement complexonates contributed to a decrease in the specific
activity of Cs-137 by more than 50% (Fig. 14, a). Both microelements showed a high radio-
blocking effect. Thus, zinc in the form of a salt solution reduced the accumulation of radio-
cesium by more than 1.5 times), and in the form of ZnEDDS – by 2.1 times. The results of the
action of trace elements on the accumulation of 90Sr in plants were distinguished, first of all, by
high coefficients of accumulation of the radionuclide (Kacum.=4.33). The influence of
microelements in the form of salts on the accumulation of 90Sr in lupine plants was manifested to
a somewhat lesser extent compared to monometallic complexonates. The most effective data, as
in the experiments with 137Cs, turned out to be in the version with the heterometallic complex
MnZnEDDS – the accumulation of radio-strontium in the vegetative mass of lupine decreased by
34% (Fig. 14, b).
Fig. 14 – Influence of microelements and their complexonates on the accumulation of 137Cs and 90Sr in
the lupine vegetative mass.
It should be noted that microelements used as microfertilizers contributed to the activation of
metabolic processes in plants through phytohormones, enzymes, vitamins, improvement of
metabolic processes in chlorophylls, contributing to the accumulation of metabolites in crops. In
The obtained results confirm the opinion
that one of the mechanisms of reducing the
accumulation of 137Сs and 90Sr by plants under
the influence of microelements can be due to
the antagonistic interactions of microelements
and the radionuclide on the one hand, and on
the other hand, to an indirect effect due to the
stimulation of the entry of macroelements into
plants – its antagonists , in particular potassi
um, calcium and possibly some other elements,
a noticeable increase in the amount of which in
plants was found during foliar treatments with
zinc, cobalt and manganese. It is likely that the
effect of the use of complexonates is associat
ed with better penetration of the trace element
through cell membranes, the ability to be di
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O. K. Trunova UCJ № 12 / Vol. 88
rectly incorporated into the molecular struc
tures of enzymatic systems, bypassing many
transport chains.
CONCLUSIONS. The role of trace elements
in plant nutrition is multifaceted. In particular,
Cu, Mo, Mn, Co, Zn, B and others increase the
activity of many enzymes and enzyme systems
in the plant body and improve the plant's use
of nutrients from the soil and fertilizers. There
fore, trace elements cannot be replaced by other
substances, and their deficiency must be filled.
Only then will we receive high-quality pro
ducts that contain the optimal amount of su
gars, amino acids, and vitamins for this vari
ety. Microelements can accelerate plant deve
lopment and seed ripening. They increase the
resistance of plants to adverse environmental
conditions (lack of moisture in the soil, increase
or decrease in temperature). In addition, they
protect plants from a number of bacterial and
fungal diseases (bacteriosis of flax, beet heart
rot, gray spotting of cereals, etc.), but unlike
the effect of toxic chemicals, this occurs due to
an increase in plant immunity.
The scientifically justified use of microele
ments in agricultural production is based not
only on the need for them of a certain crop,
but to a greater extent on their retention in the
soil. It was established that the content of trace
elements in the soil determines their content
in plants, affecting their productivity and the
quality of the yield. In this regard, the basis for
the development of measures for the produc
tion and use of microfertilizers should be the
content of microelements in the soil, their ge
ographical distribution and distribution along
the soil profile.
It has been established that trace elements
in the form of inorganic salts work satisfactori
ly only in acidic soils. In soils close to neutral,
their effectiveness decreases tenfold. In neut
ral, weakly alkaline and carbonate soils, inor
ganic salts cannot retain microelements in a
water-soluble form available to plants and their
efficiency approaches zero, i.e. they turn into
poorly soluble forms (hydroxide, carbonates)
and become unavailable to plants.
The researches of agrarian scientists and
chemical scientists established that microele
ments are most effective for plants in the form
of metal complexes (chelates). In particular, the
complexes are stable in all types of soil and there
are no soil pH restrictions for them. It should
be noted that the specific properties of various
soils and the complex physiological processes
occurring in the plant have a noticeable effect
on the action of complex compounds. In this
regard, it is difficult to assume the possibility
of creating a universal means of combating the
lack of trace elements on various soils. The most
reliable solution to this problem is the creation
of a wide range of metal chelates for their diffe
rentiated application depending on the nature
of the plant and the nature of the soil.
In addition, the use of microelement com
plexes can be an effective additional measure
to reduce the ingress of radionuclides into ag
ricultural plants, especially in biogeochemical
provinces with their deficiency.
AKNOWLEDGEMENT. The work was
carried out with the financial support
from the National Academy of Scien
ces of Ukraine within the framework
of the state budget topic «Creation of new
hybrid, composite and polymer materials
doped with coordination compounds of 3d-
and 4f-metals based on beta-diketonate and
carboxylate acyclic ligands.» The state regist
ration number of the work is 0122U001299.
132 ISSN 2708-129X. Укр. хім. журн., 2022
THE ROLE OF CHELATE COORDINATION COMPOUNDS OF BIOGENIC METALS IN THE VITAL ACTIVITY OF PLANTS.INORGANIC CHEMISTRY
РОЛЬ ХЕЛАТНИХ КООРДИНАЦІЙНИХ СПОЛУК
БІОГЕННИХ МЕТАЛІВ У ЖИТТЄДІЯЛЬНОСТІ
РОСЛИН
О. К. Трунова*
Інститут загальної та неорганічної хімії
ім. В. І. Вернадського НАН України,
просп. Академіка Палладіна, 32/34, Київ
03142, Україна
*e-mail: trelkon@gmail.com
В оглядовій статті розглянуто основні
питання створення та застосування су
часних хелатних мікродобрив на основі
мікроелементів у сільськогосподарському
виробництві. Висвітлено питання ролі мік
роелементів у життєдіяльності живих орга
нізмів та способи подолання нестачі мікро
елементів у рослинах. Представлено огляд
координаційних сполук 3d-металів (Fe,
Mn, Zn, Cu, Со, Ni, Mo) з різними класами
комплексонів, особливості їхньої будови та
властивостей. Міститься актуальний ма
теріал про використання комплексонатів
мікроелементів для створення сучасних
хелатних добрив. Приділено увагу засто
суванню комплексонатів мікроелементів
на забруднених радіонуклідами (137Сs, 90Sr)
територіях.
Ключові слова: координаційні сполуки,
мікроелементи, хелати, комплексони, доб
рива, рослини.
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Стаття надійшла 07.01.2023.
|
| id | oai:ojs2.1444248.nisspano.web.hosting-test.net:article-505 |
| institution | Ukrainian Chemistry Journal |
| keywords_txt_mv | keywords |
| language | English |
| last_indexed | 2026-07-23T01:09:13Z |
| publishDate | 2023 |
| publisher | V.I.Vernadsky Institute of General and Inorganic Chemistry |
| record_format | ojs |
| resource_txt_mv | ucjorgua/73/1d5cea52c049e08a1433553b1b19b173.pdf |
| spelling | oai:ojs2.1444248.nisspano.web.hosting-test.net:article-5052026-07-22T08:23:50Z THE ROLE OF CHELATE COORDINATION COMPOUNDS OF BIOGENIC METALS IN THE VITAL ACTIVITY OF PLANTS Trunova, Olena coordination compounds, microelements, chelates, complexones, fertilizers, plants. The review article discusses the main issues of creating and using modern chelated microfertilizers based on trace elements in agricultural production. Issues of the role of microelements in the vital activity of living organisms and methods of overcoming the lack of microelements in plants are highlighted. An overview of coordination compounds of 3d-metals (Fe, Mn, Zn, Cu, Co, Ni, Mo) with different classes of complexons, features of their structure and properties is presented. It contains relevant material on the use of microelement complexes for the creation of modern chelated fertilizers. Attention is paid to the use of trace elements complexonates in areas contaminated with radionuclides (137Сs, 90Sr). V.I.Vernadsky Institute of General and Inorganic Chemistry 2023-01-27 Article Article Inorganic Chemistry Неорганическая химия Неорганічна хімія application/pdf https://ucj.org.ua/index.php/journal/article/view/505 10.33609/2708-129X.88.12.2022.91-138 Ukrainian Chemistry Journal; Vol. 88 No. 12 (2022): Ukrainian Chemistry Journal; 91-138 Украинский химический журнал; ##issue.vol## 88 ##issue.no## 12 (2022): Ukrainian Chemistry Journal; 91-138 Український хімічний журнал; Том 88 № 12 (2022): Український хімічний журнал; 91-138 2708-129X 2708-1281 en https://ucj.org.ua/index.php/journal/article/view/505/257 Copyright (c) 2023 Olena Trunova https://creativecommons.org/licenses/by-nc/4.0 |
| spellingShingle | Trunova, Olena THE ROLE OF CHELATE COORDINATION COMPOUNDS OF BIOGENIC METALS IN THE VITAL ACTIVITY OF PLANTS |
| title | THE ROLE OF CHELATE COORDINATION COMPOUNDS OF BIOGENIC METALS IN THE VITAL ACTIVITY OF PLANTS |
| title_full | THE ROLE OF CHELATE COORDINATION COMPOUNDS OF BIOGENIC METALS IN THE VITAL ACTIVITY OF PLANTS |
| title_fullStr | THE ROLE OF CHELATE COORDINATION COMPOUNDS OF BIOGENIC METALS IN THE VITAL ACTIVITY OF PLANTS |
| title_full_unstemmed | THE ROLE OF CHELATE COORDINATION COMPOUNDS OF BIOGENIC METALS IN THE VITAL ACTIVITY OF PLANTS |
| title_short | THE ROLE OF CHELATE COORDINATION COMPOUNDS OF BIOGENIC METALS IN THE VITAL ACTIVITY OF PLANTS |
| title_sort | role of chelate coordination compounds of biogenic metals in the vital activity of plants |
| topic_facet | coordination compounds microelements chelates complexones fertilizers plants. |
| url | https://ucj.org.ua/index.php/journal/article/view/505 |
| work_keys_str_mv | AT trunovaolena theroleofchelatecoordinationcompoundsofbiogenicmetalsinthevitalactivityofplants AT trunovaolena roleofchelatecoordinationcompoundsofbiogenicmetalsinthevitalactivityofplants |