1. Study of the influence on the intensity of physiological processes when they are excluded from the nutrient medium.
2. Study of the specific role of individual microelements, mainly their participation in certain enzymatic reactions.
The second biochemical approach turned out to be more effective.
Iron was the first trace element whose necessity was discovered by Gries in 1843 - 1844.
The need for other microelements - boron, manganese, copper, zinc and molybdenum, for higher plants was established only in the 20s and 30s of the 20th century. The establishment of their necessity was facilitated by the discovery of the causes of many plant diseases that are not caused by fungal and bacterial infections - sugar beet heart rot, gray leaf spot, bronze disease, etc. All these diseases turned out to be the result of a physiological disorder caused by a lack of one or another microelement, and the disease was eliminated, as soon as the plant's need for the missing element was satisfied.
These elements play an exceptional role in metabolism. When they combine with organic substances, especially proteins, they increase their catalytic activity many times over. For example, iron in the complex heme complex in combination with a specific protein increases the catalytic activity against the activity of the iron ion by 1010 times.
Boron, aluminum, cobalt, manganese, zinc and copper increase the drought resistance of plants. And in this case, the effect of microelements is due to the influence on the colloidal-biochemical properties of protoplasm (increasing the hydrophilicity and water-holding capacity of colloids). Microelements also enhance the movement of plastic substances from leaves to generative organs.
Significant changes are caused by some microelements in the speed of passage of development stages. It was found that soaking wheat seeds in solutions of Cu, Zn, Mo, B salts significantly accelerates the passage of plants through the vernalization stage, while solutions of Fe and Mn did not have a positive effect or delayed development.
The influence of each element depends on the concentration: it affects the subsequent growth of above-ground organs and roots differently. Thus, Cu and Mo stimulate the growth of the stem and roots, while Mn and Ni stimulate only the stem, and B and Sr stimulate only the root.
Treatment of Cu seeds had a strong positive effect on the drought resistance of cotton plants. This effect is due to an increase in the water-holding capacity and suction power of leaf parenchyma cells, a change in the anatomical structure of leaves towards xerophyticity, etc. A similar effect was observed on winter wheat when seeds were treated with salts B, Cu, Mo, Co, P and K. The passage of the light stage was accelerated under the influence of B, Co, Mo, Mn, Zn, Cu and Al. Interestingly, this was observed only on long-day plants (winter wheat, oats) and did not appear on short-day plants (perilla).
Ya. V. Peive, M. Ya. Shkolnik, M. V. Katalymov, B. A. Yagodin and others made a great contribution to solving issues related to plant nutrition with microelements.
BorBoron is one of the most important microelements for plants. Its average content is 0.0001%, or 0.1 mg per 1 kg of dry weight. Dicotyledonous plants need boron most. A significant boron content was found in flowers, especially in the stigma and styles. In a cell, most of this trace element is concentrated in the cell walls. Boron enhances the growth of pollen tubes, pollen germination, and increases the number of flowers and fruits. Without it, seed ripening is disrupted. Boron reduces the activity of some respiratory enzymes and affects carbohydrate, protein and nucleic acid metabolism.
Boron uptake is strongly dependent on pH, and its distribution throughout the plant occurs predominantly through transpiration. The need for boron for plants was established a long time ago, but it is still unclear how its functions are realized: in what specific reactions it is involved and what is the mechanism of its participation in individual processes.
The role of boron is not well understood. This is due to the fact that boron, unlike most other microelements, is not part of any enzyme and is not an enzyme activator. Of great importance for the function of boron is its ability to produce complex compounds. Complexes with boric acid form simple sugars, polysaccharides, alcohols, phenolic compounds, etc. In this regard, it can be assumed that boron affects the rate of enzymatic reactions through the substrates on which the enzymes act.
Boron deficiency causes a number of diseases: heart rot of sugar beet, internal black spot of table beet and rutabaga, disease of browning of cauliflower heads, death of spikelets in wheat and even the entire embryonic ear of barley, yellowing of alfalfa, etc. It has been established that under the influence of boron a number of diseases change physiological processes: plasma hydration increases, absorption of cations and especially calcium increases, and absorption of anions decreases.
Also, with a lack of boron, the synthesis, transformation and transport of carbohydrates, the formation of reproductive organs, fertilization and fruiting are disrupted. Boron is necessary for plants throughout the entire period of their development. It cannot be reutilized and therefore, during boron fasting, first of all
growth cones die off - the most typical symptom of boron deficiency. Anatomical studies indicate cessation of cell division in the meristem. At the same time, significant disturbances in the normal arrangement of the elements of phloem and xylem are detected, up to the complete loss of conductivity by these tissues. This is the reason for the disturbances in the movement of plastic substances and, above all, sugars from leaves to the axial and reserve organs of plants found during boron starvation.
Crops most sensitive to boron deficiency: sugar and fodder beets, rapeseed, legumes, alfalfa, vegetables, apple trees, grapes.
MagnesiumIn higher plants, the average magnesium content is 0.02%. There is especially a lot of magnesium in plants short day- corn, millet, sorghum, hemp, as well as potatoes, beets, tobacco and legumes. A lot of it accumulates in young cells and growing tissues, as well as in generative organs and storage tissues. In grains, magnesium accumulates in the embryo, where its level is several times higher than the content in the endosperm and peel. The accumulation of magnesium in young tissues is facilitated by its relatively high mobility in plants, which determines its secondary use (reutilization) from aging tissues. Magnesium is transported through both xylem and phloem.
The chloroplast contains 15% of the Mg 2+ of the leaf; up to 6% of it can be contained in chlorophyll. With magnesium deficiency (starvation), the proportion of Mg 2+ in the pigment can reach even 50% of the total content in the leaf. This function of magnesium is unique: no other element can replace it in chlorophyll. Magnesium is necessary for the synthesis of protoporphyrin 9, the immediate precursor of chlorophyll.
Magnesium maintains the structure of ribosomes by binding RNA and protein. The large and small ribosomal subunits associate together only in the presence of magnesium. Hence, protein synthesis does not occur with a lack of magnesium, and even more so in its absence. Magnesium is an activator of many enzymes. Important feature magnesium is that it binds the enzyme to the substrate via a chelate bond.
Magnesium is part of phytin (organophosphate), a reserve organic substance. Responsible for energy transport, activates the enzyme, which is a catalyst for the participation of CO 2 in the process of photosynthesis.
Magnesium is essential for many enzymes in the Krebs cycle and glycolysis. It is also required for the functioning of lactic acid and alcohol fermentation enzymes.
Magnesium enhances the synthesis of essential oils, rubber, vitamins A and C.
With an increase in the level of magnesium supply in plants, the content of organic and inorganic forms of phosphorus compounds increases. This effect is likely due to the role of magnesium in activating enzymes involved in phosphorus metabolism.
The process of magnesium entry into plants may depend on the degree of plant supply with other cations. Thus, with a high content of potassium or ammonium in the soil or nutrient solution, the level of magnesium, especially in the vegetative parts of plants, decreases. In fruits, the amount of magnesium does not change or may even increase. On the contrary, with a low level of potassium or ammonium in the nutrient medium, the magnesium content in the plant increases. Calcium and manganese also act as competitors for magnesium uptake by plants.
Plants are deficient in magnesium mainly in non-sandy soils. Poor in magnesium and calcium, rich in gray soils; Chernozems occupy an intermediate position. When the pH of the soil solution decreases, magnesium enters the plants in smaller quantities.
A lack of magnesium leads to a decrease in the phosphorus content in plants, even if phosphates are present in sufficient quantities in the nutrient substrate, especially since phosphorus is transported throughout the plant mainly in organic form. Therefore, magnesium deficiency will inhibit the formation of organophosphorus compounds and, accordingly, the distribution of phosphorus in the plant body.
With a lack of magnesium, the formation of plastids is disrupted: the chloroplast matrix becomes clear, the grana stick together. Spots and stripes of light green appear between the green veins, and then yellow color. The edges of the leaf blades become yellow, orange, red or dark red, and this “marbled” color of the leaves, along with chlorosis, is a characteristic sign of magnesium deficiency. At later stages of magnesium starvation, light yellow and whitish stripes are also observed on young leaves, indicating the destruction of chloroplasts and then carotenoids in them, and the leaf areas adjacent to the vessels remain green longer. Subsequently, chlorosis and necrosis develop, primarily affecting the tops of the leaves.
Signs of magnesium deficiency first appear on old leaves and then spread to young leaves and plant organs. High and prolonged illumination increases signs of magnesium deficiency.
Crops sensitive to magnesium deficiency: sugar beets, potatoes, hops, grapes, nuts, greenhouse crops.
IronIn compounds containing heme (all cytochromes, catalase, peroxidase) and in non-heme form (iron-sulfur centers), iron takes part in the functioning of the main redox systems of photosynthesis and respiration. Together with molybdenum, iron participates in the reduction of nitrates and in the fixation of molecular nitrogen by nodule bacteria, being part of nitrate reductase and nitrogenase. Iron also catalyzes the initial stages of chlorophyll synthesis. Therefore, insufficient supply of iron to plants under waterlogging conditions and on carbonate soils leads to a decrease in the intensity of respiration and photosynthesis and is expressed in yellowing of leaves (chlorosis) and their rapid falling. If iron becomes unavailable for vegetative plants, then chlorosis appears only on newly developing organs. Consequently, iron is tightly bound in cells and is not able to move from old tissues to young ones. Iron is also necessary for colorless plants - fungi and bacteria, so its role is not limited only to participation in the formation of chlorophyll.
In cereal crops, chlorosis appears as alternating yellow and green stripes along the leaf. In some cases, iron deficiency can cause the death of young shoots.
Iron deficiency also causes changes in root morphology, inducing the growth of root hairs that abundantly cover the root surface. This promotes better contact with the soil and soil solution, increasing iron absorption.
Along with iron, catalytically active compounds, plant tissues can include this element in reserve substances. One of them is the protein ferritin, which contains iron in non-heme form. Iron may account for about 23% of the dry weight of ferritin. Ferritin is present in large quantities in plastids.
Crops sensitive to iron deficiency: corn, legumes, potatoes, cabbage, tomatoes, grapes, fruit and citrus fruits, ornamental crops.
ManganeseBertrand (1897) was the first to draw attention to the need for manganese in plants. Its average content is 0.001% or 1 mg per 1 kg of dry tissue mass. It enters cells in the form of Mn 2+ ions. Manganese accumulates in leaves. The participation of ions of this metal in the release of oxygen (photodecomposition of water) and the reduction of CO 2 during photosynthesis has been established. Manganese helps increase the content of sugars and their outflow from the leaves. Manganese ions activate enzymes that catalyze the reactions of the Krebs cycle (malic acid dehydrogenase, citric acid, oxaloacetic acid decarboxylase, etc.). In this regard, the great importance of manganese for the respiration process, especially its aerobic phase, is clear.
Manganese is of great importance for the normal exchange of nitrogenous compounds. Manganese takes part in the process of reducing nitrates to ammonia. This process goes through stages catalyzed by a number of enzymes, of which two (hydroxylamine reductase and nitrite reductase) are dependent on manganese, and therefore plants lacking manganese cannot use nitrates as a source of nitrogen nutrition.
Manganese activates enzymes involved in the oxidation of the most important phytohormone - auxin.
This element plays a specific role in maintaining the structure of chloroplasts. In the absence of manganese, chlorophyll is quickly destroyed in light.
Despite the significant content of manganese in the soil, most of it is difficult for plants to access, especially in soils with a neutral pH value.
Manganese is responsible for the oxidation of iron in plants to non-toxic compounds. It is a necessary component of the synthesis of vitamin C. Intensifies the accumulation of sugar in the roots of sugar beets and protein in grain crops. Responsible for the process of nitrogen absorption. It is an activator of photosynthesis after plants freeze.
A symptom of a disease caused by manganese deficiency is primarily the appearance of chlorotic spots between the leaf veins. Grasses develop elongated stripes of chlorotic tissue gray, then a narrow zone of weakened turgor appears, as a result of which the leaf blade hangs down. With severe manganese deficiency, these symptoms extend to the stem. Diseased leaves turn brown and die as the disease develops.
Gray spot disease is widespread in humus-rich soils that have an alkaline reaction. Cereals are susceptible to this disease, especially oats, wheat, rye, and corn.
In plants with reticulate leaf veining, with a lack of manganese, chlorotic spots appear scattered throughout the leaf, mostly on lower leaves than on the top ones.
In beets, manganese deficiency causes a disease known as spotted jaundice. Yellow chlorotic areas appear on the leaves, then the edges of the leaves curl upward.
In peas with a lack of manganese, seed spotting develops. This disease is expressed in the appearance of brown and black spots on pea seeds or even cavities on the inner surfaces of the cotyledons.
Chlorosis also develops with a very high manganese content; in this case, manganese oxidizes iron into an insoluble oxide form and chlorosis develops from a lack of iron. Excess iron causes symptoms of manganese deficiency. The most favorable ratios of iron and manganese for better growth plants and general health 2:1.
Crops sensitive to manganese deficiency: cereal grains (wheat, barley, oats), corn, peas, soybeans, potatoes, sugar beets, cherries, citrus fruits.
ZincThe zinc content in the above-ground parts of legumes and cereal plants is 15 - 60 mg per 1 kg of dry weight. Increased concentrations are observed in leaves, reproductive organs and growth cones, the highest in seeds. Zinc enters the plant in the form of the Zn 2+ cation, having a multifaceted effect on metabolism. It is necessary for the functioning of a number of glycolytic enzymes. The role of zinc is also important in the formation of the amino acid tryptophan. This is precisely why zinc influences the synthesis of proteins, as well as the phytohormone indolylacetic acid (auxin), the precursor of which is tryptophan. Fertilizing with zinc helps to increase the content of auxins in tissues and activates their growth. Zinc plays an important role in DNA and RNA metabolism, protein synthesis and cell division. It is an enzyme activator and prevents premature cell aging. Helps increase heat, drought and frost resistance of plants. Zinc has long been considered as a stimulant and only in the 30s. last century, the unconditional necessity of this element for all higher plants was established. Zinc deficiency disease is widespread among fruit trees. With zinc deficiency, instead of normally elongated shoots with well-developed leaves, diseased plants form a rosette of small, crowded, hard leaves in the spring. Different fruit disease is designated differently: small leaves, rosette disease, spotted chlorosis, jaundice. Zinc is involved in redox processes and is associated with the transformation of compounds containing a sulfhydryl group. Lack of zinc causes suppression of carbohydrate metabolism processes, since zinc deficiency most strongly affects plants rich in carbohydrates. Also, with zinc deficiency in plants, phosphorus metabolism is disrupted: phosphorus accumulates in the root system, its transport to above-ground organs is delayed, the conversion of phosphorus into organic forms slows down - the content of inorganic phosphates increases several times, the content of phosphorus in the composition of nucleotides, lipids and nucleic acids decreases. In addition, the rate of cell division is suppressed 2-3 times, which leads to morphological changes in leaves, impaired cell elongation and tissue differentiation.
Crops that are especially sensitive to zinc deficiency: corn, soybeans, beans, hops, potatoes, flax, green vegetables, grapes, apple and pear trees, citrus fruits.
MolybdenumThe highest molybdenum content is typical for legumes (0.5 - 20 mg per 1 kg of dry weight), cereals contain from 0.2 to 2.0 mg of molybdenum per 1 kg of dry weight. It enters plants as the MoO 4 2- anion and is concentrated in young, growing organs. It is more abundant in leaves than in roots and stems, and in leaves it is concentrated mainly in chloroplasts.
Molybdenum takes part in the reduction of nitrates, being part of nitrate reductase, and is also a component of the active center of nitrogenase in bacteroids that fix atmospheric nitrogen in legume nodules.
Helps increase the content of chlorophyll, carbohydrates, carotene, ascorbic acid and protein substances.
Molybdenum is part of more than 20 enzymes, performing not only a catalytic, but also a structural function.
With a lack of Mo, it accumulates in tissues a large number of nitrates, nodules on the roots of legumes do not develop, plant growth is inhibited, and deformation of the leaf blades is observed. Molybdenum, like iron, is necessary for the biosynthesis of leghemoglobin (leghemoglobin), an oxygen carrier protein in legume nodules. When there is a deficiency, the nodules become yellow or gray, but their normal color is red.
With a lack of molybdenum, the content of ascorbic acid drops sharply, and disturbances in the phosphorus metabolism of plants are observed.
In plants that are deficient in molybdenum, light spots appear on the leaves, buds may die, fruits and tubers crack.
Plant growth is inhibited and due to impaired chlorophyll synthesis, plants appear pale green. These signs are similar to those of nitrogen deficiency.
Crops sensitive to molybdenum deficiency: cereal grains, legumes, sugar beets, tomatoes, cabbage, alfalfa.
Other trace elementsIncluded different types More than 60 elements have been found in plants, of which, in addition to those noted above, sodium, silicon, chlorine, cobalt, copper, and aluminum are also considered by some authors to be essential.
Found in a plant silicon impregnates cell walls and makes them hard and resistant to damage by insects and protects cells against fungal infection. Silicon is also necessary for the growth of diatoms.
Chlorine considered a stimulator of enzyme activity. Chlorine is important for green photosynthetic plants. There is information about the effect of chlorine on nitrogen metabolism. Concentrating in the plant in vacuoles, chlorides can perform an osmoregulatory function. Chlorine deficiency is rare and is observed only on very alkaline soils.
Action aluminum seen as a catalyst. In addition, with some excess accumulation of aluminum in the plant, the color of the flowers changes. For example, aluminum accumulation in a Hydrangea plant changes normally red or white flowers to blue or purple.
Sodium accumulates in plants in significant quantities, but does not play a significant role in their life, since it can be completely excluded from nutrient solution. However, for halophytes, plants in saline areas, the presence of sodium favors growth.
Content cobalt the average is 0.00002%. Cobalt is especially necessary for leguminous plants, since it is involved in the fixation of atmospheric nitrogen. Cobalt is part of cobalamin (vitamin B12 and its derivatives), which is synthesized by bacteria in nodules leguminous plants, as well as in the composition of enzymes in nitrogen-fixing organisms involved in the synthesis of methionine, DNA and bacterial cell division. With cobalt deficiency, leghemoglobin synthesis is suppressed, protein synthesis is reduced, and the size of bacteroids is reduced. This speaks in favor of the need for cobalt. The need for cobalt has been established for higher plants that are not capable of nitrogen fixation. The influence of cobalt on the functioning of the photosynthetic apparatus, protein synthesis, and its connection with auxin metabolism is shown. The difficulty in deciding whether cobalt is necessary for all plants is that the need for it is extremely small.
Copper activates the formation of proteins and B vitamins. Like zinc, it activates the enzyme and prevents premature aging of plant cells. Takes part in the metabolism of proteins and carbohydrates in the plant. Significantly increases the plant's immunity to fungal and bacterial diseases. There is very little of this element in sandy and peaty soils. Copper deficiency manifests itself in persistent wilting of the upper leaves, even with a good supply of moisture, until they fall off. The edges of young leaves die off, followed by chlorosis and curling; The release of pollen grains slows down, resulting in reduced pollination of plants. There is a significant decrease in crop yield (if there are no visual signs of microelement deficiency); lodging may occur in cereal crops; fruit crops may experience drooping branches and crowns.
IRON
Iron plays a leading role among all heavy metals contained in plants.
This is evidenced by the fact that it is contained in plant tissues in quantities
properties more significant than other metals. So the iron content in the leaves is
indicates hundredths of a percent, followed by manganese, the concentration of zinc is expressed
already in thousandths, and the copper content does not exceed ten-thousandths of a percent.
Organic compounds, which include iron, are necessary in biochemical
chemical processes occurring during respiration and photosynthesis. This is explained very
high degree of their catalytic properties. Inorganic compounds iron also
capable of catalyzing many biochemical reactions, and in combination with organic
With these substances, the catalytic properties of iron increase many times.
The catalytic effect of iron is associated with its ability to change the degree
oxidation. The iron atom is oxidized and reduced relatively easily, therefore
Iron compounds are electron carriers in biochemical processes. IN
The basis of the reactions occurring during plant respiration is the process of transfer of electrical energy.
new This process is carried out by enzymes - dehydrogenesis and cytochromes, co-
holding iron.
Iron has a special function - its indispensable participation in the biosynthesis of chlo-
rofilla. Therefore, any reason that limits the availability of iron for plants
leads to serious diseases, in particular chlorosis.
When photosynthesis and respiration are impaired and weakened due to insufficient
formation of organic substances from which the plant organism is built, and deficiency
organic reserves, a general metabolic disorder occurs. Therefore, when
Acute iron deficiency inevitably leads to plant death. At trees and bushes
nicks, the green color of the apical leaves disappears completely, they become almost
white and gradually dry out.
MANGANESE
The role of manganese in plant metabolism is similar to the functions of magnesium and iron.
behind. Manganese activates numerous enzymes, especially during phosphorylation.
Since manganese activates enzymes in the plant, its deficiency affects
many metabolic processes, in particular the synthesis of carbohydrates and proteins.
Signs of manganese deficiency in plants are most often observed in carbonate-
ny, highly limed, as well as on some peaty and other soils at pH
above 6.5.
Manganese deficiency becomes noticeable first on young leaves over
light green color or discoloration (chlorosis). Unlike glandular
chlorosis in monocots, gray, gray-green-colored leaves appear in the lower part of the leaf blade.
Lean or brown, gradually merging spots, often with a darker border.
Signs of manganese starvation in dicotyledons are the same as with iron deficiency,
only the green veins usually do not stand out so sharply on yellowed tissues. Except
In addition, brown necrotic spots appear very quickly. Leaves die even if...
faster than with iron deficiency.
Manganese deficiency in plants worsens at low temperatures and
high humidity. Apparently, in this regard, winter grains are most sensitive to its
deficiency in early spring.
Manganese is involved not only in photosynthesis, but also in the synthesis of vitamin C. If not
In the presence of manganese, the synthesis of organic substances decreases, the content of
chlorophyll in plants, and they develop chlorosis.
Symptoms of manganese deficiency in plants most often appear on
carbonate, peaty and other soils with a high content of organic matter
society. A lack of manganese in plants manifests itself in the appearance of small
chlorotic spots located between the veins, which remain green. U
In cereals, chlorotic spots look like elongated stripes, and in beets they are located
appear in small spots on the leaf blade. With manganese starvation there is
also poor development of the plant root system. The most sensitive cultures
Examples of manganese deficiency include sugar beet, fodder beet, table beet, oats, car-
poplar, apple, cherry and raspberry. In fruit crops, along with chlorotic disease,
With the loss of leaves, weak foliage of trees is noted, earlier than usual
falling leaves, and with severe manganese starvation - drying and death of the ver-
hushek branches.
The physiological role of manganese in plants is associated, first of all, with its participation
sty in the redox processes taking place in a living cell, it
is part of a number of enzyme systems and takes part in photosynthesis, respiration, carbon
water and protein metabolism, etc.
The study of the effectiveness of manganese fertilizers on various soils in Ukraine has shown
stated that the yield of sugar beets and the sugar content in them were higher compared to their background, more
At the same time, the grain harvest was also higher.
ZINC
All cultivated plants in relation to zinc they are divided into 3 groups:
- very sensitive (corn, flax, hops, grapes, fruit);
- moderately sensitive (soybeans, beans, forage legumes, peas, sugar beets,
sunflowers, clover, onions, potatoes, cabbage, cucumbers, berries);
- weakly sensitive (oats, wheat, barley, rye, carrots, rice, alfalfa).
A lack of zinc for plants is most often observed on sandy and carbonic soils.
native soils. .Little available zinc on peatlands, as well as on some low-
fertile soils. Zinc deficiency has the greatest effect on the formation of semen.
myan than on development vegetative organs. Symptoms of zinc deficiency
roko are found in various fruit crops (apple, cherry, Japanese plum,
nut, pecan, apricot, avocado, lemon, grapes). They especially suffer from a lack of zinc-
as citrus crops.
The physiological role of zinc in plants is very diverse. It causes pain
significant influence on redox processes, the speed of which at its
deficiency is noticeably reduced. Zinc deficiency leads to disruption of pre-
rotation of hydrocarbons. It has been established that with a lack of zinc in leaves and roots,
mat, citrus and other crops, phenolic compounds, phytoste-
rolls or lecithins, the starch content decreases. .
Zinc is part of various enzymes: carbonic anhydrase, triose phosphate de-
hydrogenases, peroxidases, oxidases, polyphenoloxidases, etc.
It was found that large doses of phosphorus and nitrogen increase the signs of deficiency.
accuracy of zinc in plants and that zinc fertilizers are especially necessary when introducing
research of high doses of phosphorus.
The importance of zinc for plant growth is closely related to its participation in nitrogen metabolism.
me. Zinc deficiency leads to a significant accumulation of soluble nitrogen compounds
compounds - amines and amino acids, which disrupts protein synthesis. Many studies
confirmed that the protein content in plants with a lack of zinc decreases.
Under the influence of zinc, the synthesis of sucrose, starch, and the total content of
carbohydrates and proteins. The use of zinc fertilizers increases the content
reduction of ascorbic acid, dry matter and chlorophyll. Zinc fertilizers increase
determine the drought, heat and cold resistance of plants.
Agrochemical studies have established the need for zinc for large
number of species of higher plants. Its physiological role in plants is multi-
third party. Zinc plays an important role in redox processes,
occurring in the plant body, it is an integral part of enzymes,
directly participates in the synthesis of chlorophyll, affects carbohydrate metabolism in the
tenia and promotes the synthesis of vitamins.
With zinc deficiency, plants develop chlorotic spots on their faces.
leaves that turn pale green and, in some plants, almost white. U
Apple, pear and walnut trees with a lack of zinc develop the so-called rosette
a disease expressed in the formation of small leaves at the ends of branches that spread
are placed in the form of a rosette. During zinc starvation, fruit buds become
there is little. The yield of pome fruits drops sharply. Sweet cherries are even more sensitive to
lack of zinc than apple and pear. Signs of zinc starvation in cherries manifested
This results in the appearance of small, narrow and deformed leaves. Chlorosis first appeared
appears on the edges of the leaves and gradually spreads to the midrib of the leaf. At
When the disease develops strongly, the entire leaf turns yellow or white.
Among field crops, zinc deficiency most often manifests itself in corn
ruse in the form of the formation of a white sprout or whitening of the top. Zinc index
starvation in legumes (beans, soybeans) is the presence of chlorosis on the leaves, sometimes asymmetric
metric development of the leaf blade. Zinc deficiency for plants is most often
observed on sandy and sandy loam soils with low content, as well as
carbonate and old arable soils.
The use of zinc fertilizers increases the yield of all field, vegetable and
fruit crops. At the same time, there is a decrease in the infestation of plants by fungal
diseases, the sugar content of fruit and berry crops increases.
BOR
Boron is necessary for the development of the meristem. Characteristic signs of boron deficiency
are the death of growth points, shoots and roots, disturbances in the formation and development
tia of the reproductive organs, destruction of vascular tissue, etc. Boron deficiency is very
often causes destruction of young growing tissues.
Under the influence of boron, the synthesis and movement of carbohydrates, especially sugar, improves.
charose, from leaves to fruiting organs and roots. It is known that monocot races
Tenias are less demanding on boron than dicotyledons.
There is evidence in the literature that boron improves the movement of growth
substances and ascorbic acid from the leaves to the fruiting organs. Determined that
flowers are the richest in boron compared to other parts of plants. He plays
significant role in fertilization processes. If it is excluded from the diet
environment, plant pollen germinates poorly or even not at all. In these cases, entering
boron promotes better germination of pollen, eliminates the fall of ovaries and enhances
promotes the development of reproductive organs.
Boron plays an important role in cell division and protein synthesis and is essential
a major component of the cell membrane. Boron performs an extremely important function
in carbohydrate metabolism. Its deficiency in the nutrient medium causes the accumulation of sugar
ditch in plant leaves. This phenomenon is observed in those most responsive to boron
crop fertilizers. Boron promotes and better use calcium in processes
metabolism in plants. Therefore, with a lack of boron, plants cannot normalize
It is not appropriate to use calcium, although the latter is found in the soil in sufficient quantities.
honor. It has been established that the amount of boron absorption and accumulation by plants aged
melt when potassium in the soil increases.
With a lack of boron in the nutrient medium, a violation of the anatomical
structure of plants, for example, poor development of xylem, fragmentation of flosis
we are the main parenchyma and degeneration of the cambium. The root system develops poorly,
since boron plays a significant role in its development.
A lack of boron leads not only to a decrease in agricultural yields
crops, but also to a deterioration in its quality. It should be noted that boron is necessary for plants
niyamas throughout growing season. Exclusion of boron from the nutrient medium in
any phase of plant growth leads to its disease.
External signs boron starvation varies depending on the type of plant
However, we can cite a number of general signs that are characteristic of most
properties of higher plants. In this case, the growth of the root and stem stops,
then chlorosis of the apical point of growth appears, and later, with severe boron starvation,
its complete death follows. From the axils of the leaves, lateral shoots develop,
The shade bushes vigorously, but the newly formed shoots soon also stopped.
growth and all the symptoms of the disease of the main stem are repeated. Especially
the reproductive organs of plants suffer greatly from a lack of boron, while
A plant may not form flowers at all, or very few flowers are formed.
Lo, the barren flower is marked by the fall of the ovaries.
In this regard, the use of boron-containing fertilizers and improved provision
of plants this element contributes not only to an increase in yield, but also to a significant
significant improvement in product quality. Improved boron nutrition leads to increased
reducing the sugar content of sugar beets, increasing the content of vitamin C and sugars
V fruit and berry crops, tomatoes, etc.
Most responsive to boron fertilizers sugar and fodder beets, alfalfa and
ver (seed crops), vegetable crops, flax, sunflower, hemp, essential oil-
grains and crops.
COPPER
Different crops have different sensitivities
to copper deficiency. Plants can be arranged in the following descending order
responsiveness to copper: wheat, barley, oats, flax, corn, carrots, beets, onions, spinach
nat, alfalfa and White cabbage. Potatoes are characterized by average responsiveness,
tomato, red clover, beans, soybeans. Varietal features plants within one
and also the species are of great importance and significantly influence the degree of manifestation
symptoms of copper deficiency. .
Copper deficiency often coincides with zinc deficiency, and on sandy soils
also with magnesium deficiency. Application of high doses nitrogen fertilizers enhances
the need of plants for copper and contributes to the exacerbation of symptoms of copper deficiency
ness.
Despite the fact that a number of other macro- and microelements have a large
influence on the rate of redox processes, the effect of copper in these
reactions is specific and cannot be replaced by any other
element. Under the influence of copper, both the activity of peroxysilase increases and decreases
decrease in the activity of synthetic centers and leads to the accumulation of soluble carbohydrates,
amino acids and other breakdown products of complex organic substances. Copper is
an integral part of a number of important oxidative enzymes - polyphenol oxidase, ac-
corbinate oxidase, lactase, dehydrogenase, etc. All of these enzymes carry out
They cause oxidation reactions by transferring electrons from the substrate to molecular oxygen,
which is an electron acceptor. In connection with this function, the valency of copper in
redox reactions changes from divalent to monovalent
tape state and vice versa.
Copper plays an important role in photosynthesis processes. Under the influence of copper, increased
Both the activity of paroxidase and the synthesis of proteins, carbohydrates and fats are affected. When she doesn't
In affluence, the destruction of chlorophyll occurs much faster than under normal conditions.
At a certain level of plant nutrition with copper, there is a decrease in the activity of synthetic
processes, which leads to the accumulation of soluble carbohydrates, amino acids and other pro-
decomposition products of complex organic substances.
When fed with ammonia nitrogen, a lack of copper delays the incorporation of nitrogen into
protein, peptones and peptides already in the first hours after applying nitrogen fertilizing. This
indicates the particularly important role of copper in the use of ammonia nitrogen.
A characteristic feature of the action of copper is that this trace element
increases plant resistance against fungal and bacterial diseases. Copper
reduces diseases of grain crops various types smut, increases resistance
susceptibility of plants to brown spot, etc. .
Signs of copper deficiency appear most often in peaty and
acidic sandy soils. Symptoms of plant diseases due to a lack of copper in the soil
For cereals, they manifest themselves in the whitening and drying of the tips of the leaf blade. At
severe copper deficiency, plants begin to bush intensively, but subsequently
no shedding occurs and the entire stem gradually dries out.
Fruit crops with a lack of copper develop the so-called dryover disease.
splint or exanthema. At the same time, on the leaf blades of plums and apricots between
the veins develop a distinct chlorosis.
In tomatoes with a lack of copper, there is a slowdown in shoot growth, weak
development of roots, appearance of dark bluish-green color of leaves and their curling
tion, lack of flower formation.
All of the above diseases of agricultural crops when applied
copper fertilizers are completely eliminated, and plant productivity increases dramatically
.
MOLYBDENUM
Currently, molybdenum, in terms of its practical importance, is one of the
first places among other microelements, since this element turned out to be very important
factor in solving two cardinal problems of modern agriculture -
supply - providing plants with nitrogen and farm animals with protein.
The necessity of molybdenum for plant growth has now been established.
at all. With a lack of molybdenum, large amounts accumulate in plant tissues.
nitrates and normal nitrogen metabolism is disrupted.
Molybdenum is involved in hydrocarbon metabolism, in the exchange of phosphate fertilizers,
in the synthesis of vitamins and chlorophyll, affects the intensity of redox
body reactions. After treating seeds with molybdenum, the content of leaves increases
reduction of chlorophyll, carotene, phosphorus and nitrogen.
It has been established that molybdenum is part of the enzyme nitrate reductase,
carrying out the reduction of nitrates in plants. The activity of this enzyme depends
on the level of provision of plants 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 activity.
The introduction of molybdenum separately and together with boron in various phases of the growth of
Roja improved the activity of ascorbate oxidase, polyphenol oxidase and paroxidase.
The greatest effect on the activity of ascorbate oxidase and polyphenol oxidase is
calls molybdenum, and the activity of paroxidase is boron against the background of molybdenum.
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 so-
holding proteins in plants.
Under the influence of molybdenum in plants, the content of carbohydrates also increases.
additives, carotene and ascorbic acid, the content of protein substances increases.
Exposure to molybdenum in plants increases the content of chlorophyll and increases
The intensity of photosynthesis decreases.
A lack of molybdenum leads to profound metabolic disorders in races.
shadows. Symptoms of molybdenum deficiency are preceded primarily by
changes in nitrogen metabolism in plants. If there is a lack of molybdenum, the process is inhibited
biological reduction of nitrates, the synthesis of amides, amino acids and proteins slows down.
All this leads not only to a decrease in yield, but also to a sharp deterioration in its quality.
.
The importance of molybdenum in plant life is quite diverse. It activates
processes of fixation of atmospheric nitrogen by nodule bacteria, promotes
synthesis and metabolism of protein substances in plants. Most sensitive to deficiency
molybdenum such crops as soybeans, legumes, clover, perennial
herbs. The need of plants for molybdenum fertilizers usually increases in acidic conditions.
soils having a pH below 5.2.
The physiological role of molybdenum is associated with the fixation of atmospheric nitrogen, re-
production of nitrate nitrogen in plants, participation in redox
processes, carbohydrate metabolism, in the synthesis of chlorophyll and vitamins.
The lack of molybdenum in plants is manifested in the light green color of the leaves.
stems, while the leaves themselves become narrow, their edges curl inward and
foams die off, mottling appears, leaf veins remain light green. Not-
the abundance of molybdenum is expressed, first of all, in the appearance of a yellow-green color of the
stems, which is a consequence of weakening atmospheric nitrogen fixation, stems and
The heads of the plants turn reddish-brown.
The results of experiments on the study of molybdenum fertilizers showed that when they
application increases the yield of agricultural crops and its quality, but especially
Its role in the intensification of symbiotic nitrogen fixation by legume crops is especially important.
tours and improving the nitrogen nutrition of subsequent crops.
COBALT
Cobalt is necessary to enhance the nitrogen-fixing activity of nodule bacteria.
terium It is part of vitamin B12, which is present in the nodules, has a
a significant positive effect on the activity of the hydrogenase enzyme, as well as an increase
checks the activity of nitrate reductase in the nodules of legumes.
This microelement affects the accumulation of sugars and fats in plants. Cobalt
has a beneficial effect on the process of chlorophyll synthesis in plant leaves, reduces
its disintegration in the dark increases the intensity of respiration, ascorbic acid content
acids in plants. As a result foliar feeding cobalt in the leaves of the plant
This increases the total content of nucleic acids. Cobalt has a noticeable
positive effect on the activity of the hydrogenase enzyme, and also increases the activity
nitrate reductase activity in legume nodules. Positive effect has been proven
the effect of cobalt on tomatoes, peas, buckwheat, barley, oats and other crops. .
Cobalt takes an active part in oxidation and reduction reactions,
stimulates the Krebs cycle and has a positive effect on breathing and energy
chemical metabolism, as well as protein biosynthesis of nucleic acids. Thanks to its position
significant effect on metabolism, protein synthesis, carbohydrate absorption, etc. he is
is a powerful growth stimulant.
The positive effect of cobalt on agricultural crops is
is in enhancing nitrogen fixation by legumes, increasing the chlorophyll content in leaves
food and vitamin B12 in the nodules. .
The use of cobalt in the form of fertilizers for field crops increased the yield
sugar beets, grain crops and flax. When fertilizing grapes with cobalt,
The harvest of its berries, their sugar content, and acidity decreased.
Table 1 shows generalized characteristics of the influence of microelements on
functions of plants, their behavior in soil under different conditions, symptoms of their deficiency
quote and its consequences.
The given overview of the physiological role of microelements for higher plants
indicates that the deficiency of almost each of them leads to the manifestation of chlorosis in plants to varying degrees.
On saline soils, the use of microelements enhances the absorption of
decreases nutrients from the soil and reduces the absorption of chlorine, increases the
accumulation of sugars and ascorbic acid, there is a slight increase in the content
decreases chlorophyll and increases the productivity of photosynthesis. In addition, it is necessary
note the fungicidal properties of microelements, suppression of fungal diseases
when processing seeds and when applying them to vegetative plants.
The functions of each macro- and microelement in plants are strictly specific; no element can be replaced by another. A deficiency of any macro- and microelement leads to disruption of metabolism and physiological processes in plants, deterioration of their growth and development, reduction in yield and its quality. With an acute deficiency of nutrients, plants develop characteristic signs of starvation.
Nitrogen is part of amino acids, amides, proteins, enzymes, nucleic acids, chlorophyll, alkaloids, phosphatides, most vitamins and other organic nitrogenous compounds that play an important role in metabolic processes in the plant.
IN natural conditions Plant nutrition with nitrogen occurs through their consumption nitrate ion And ammonium cation, located in the soil solution and in the state exchange-absorbed by soil colloids. Mineral forms of nitrogen entering plants undergo a complex cycle of transformations, ultimately being included in the composition of organic compounds - amino acids, amides and, finally, protein.
Nitrate nitrogen can accumulate in significant quantities in plants without causing harm to them. However, the content of nitrates in feed, vegetables and other plant products above a certain limit has a harmful effect on the body of animals and humans consuming such products.
With a sufficient amount of carbohydrates, ammonia nitrogen, which enters plants from the soil and formed during the reduction of nitrates, joins organic keto acids - products of incomplete oxidation of carbohydrates (oxaloacetic, ketoglutaric or fumaric), forming primary amino acids (aspartic and glutamic). This process is called direct amination and is the main way in which amino acids are formed.
All other amino acids that make up the protein (more than 20) are synthesized transamination of aspartic and glutamic acids. In the process of transamination, under the action of enzymes, the amino groups of these and other amino acids are transferred to other keto acids. Transamination is of great importance for protein synthesis, and also for deamination of amino acids– cleavage of an amino group from an amino acid, resulting in the formation of ammonia and keto acid. The latter is used by plants for processing into carbohydrates, fats and other substances, and ammonia is again involved in the synthesis of amino acids.
Play a major role in nitrogen metabolism amides – asparagine And glutamine, which are formed by adding one more ammonia molecule to aspartic and glutamic acids. As a result of the formation of amides, ammonia is disinfected, which accumulates with abundant ammonia nutrition and a lack of carbohydrates in plants.
During the growth and development of plants, a huge number of different proteins are constantly synthesized. For protein synthesis, like other complex organic compounds, requires large amounts of energy. The main sources of energy in plants are photosynthesis and respiration (oxidative phosphorylation), therefore there is a close relationship between protein synthesis and the intensity of respiration and photosynthesis.
Along with synthesis in plants, protein breakdown into amino acids with the elimination of ammonia under the action of proteolytic enzymes. In young growing organs and plants, protein synthesis exceeds breakdown; as they age, breakdown processes become more active and begin to prevail over synthesis.
Thus, the complex cycle of synthesis of organic nitrogenous substances in plants begins with ammonia, and their decomposition ends with its formation. D. N. Pryanishnikov said that “... ammonia is the alpha and omega in the metabolism of nitrogenous substances in plants.”
Nitrogen nutrition conditions greatly influence the growth and development of plants. With a lack of nitrogen their growth deteriorates sharply. The lack of nitrogen has a particularly strong effect on the development of leaves: they are small, light green in color, turn yellow prematurely, and with acute and prolonged nitrogen starvation they die, the stems become thin and weakly branch. The formation and development of reproductive organs and grain filling also deteriorate.
With normal nitrogen nutrition, the synthesis of organic nitrogenous substances increases. Plants form powerful leaves and stems with an intense green color, grow and bush well, and the formation and development of reproductive organs improves. The result is a dramatic increase in yield and protein content. However, one-sided excess nitrogen nutrition, especially in the second half of the growing season, delays plant maturation; they produce a large vegetative mass, but few grains or tubers and roots. Excessive nitrogen nutrition also worsens product quality. In the root crops of sugar beets, the concentration of sugar decreases and the content of non-protein nitrogen, “harmful” during the sugaring process, increases, in potatoes the starch content decreases, and quantities of nitrates that are dangerous for humans and animals accumulate in vegetables and feed.
Phosphorus is one of essential elements plant nutrition. Plants consume it mainly in the form of anions H 2 PO 4 (or) from salts phosphoric acid (H 3 PO 4), as well as from salts of polyphosphoric acids after their hydrolysis.
Phosphorus entering plants is included in various organic compounds. Phosphorus is included in nucleic acids And nucleoproteins, which are involved in the construction of the cytoplasm and nucleus of cells. It is contained in fitina(storage substance of the seed), which is used as a source of phosphorus during germination, as well as in phosphatides, sugar phosphates, vitamins and many enzymes.
They are also present in small quantities in plant tissues. inorganic phosphates, which play an important role in creating a buffer system of cell sap and serve as a phosphorus reserve for the formation of various organophosphorus compounds.
In a plant cell, phosphorus plays an extremely important role in energy metabolism and is involved in many processes of metabolism, division and reproduction. The role of this element is especially great in carbohydrate metabolism, in the processes of photosynthesis, respiration and fermentation.
The most diverse transformations of carbohydrates in a plant begin with addition of phosphoric acid to carbohydrate molecules or its elimination, that is, with their phosphorylation or dephosphorylation. In this case, adenosine triphosphoric acid (ATP) and other energy-rich phosphorus compounds play a particularly important role.
The large role of phosphorus in carbohydrate metabolism determines the positive effect of phosphorus fertilizers on the accumulation of sugar in sugar beets and other root crops, starch in potato tubers, etc. Phosphorus also plays an important role in the metabolism of nitrogenous substances in the plant. The reduction of nitrate nitrogen to ammonia, the formation of amino acids, their deamination and transamination occur with the participation of phosphorus. This determines the close relationship between nitrogen and phosphorus nutrition of plants. With a lack of phosphorus, protein synthesis is disrupted and its content in plants decreases.
Phosphorus is most found in reproductive and young growing organs and parts of plants, where intensive synthesis of organic matter occurs. From older leaves it can move to growth zones and be reused, so external signs of its deficiency appear in plants, primarily on older leaves. In this case, they acquire a characteristic red-violet or bluish tint, sometimes a dark green color (for example, in potatoes).
Plants are most sensitive to phosphorus deficiency at a very early age, when their root system with low absorption capacity. The negative consequences of phosphorus deficiency during this period cannot be corrected in the future even by abundant phosphorus nutrition. Therefore, providing plants with phosphorus in an easily accessible form at the beginning of the growing season, as well as throughout it, is extremely important for growth, development and crop formation. This is achieved by a combination of various methods of applying fertilizers - basic, pre-sowing and fertilizing.
Potassium also one of the main elements mineral nutrition. The physiological functions of potassium in the plant body are varied. It has a positive effect on the physical state of cytoplasmic colloids, increases their water content, swelling and viscosity, which creates normal metabolic conditions in fiber and increases plant resistance to drought.
Potassium has a positive effect on the intensity of photosynthesis, oxidative processes and the formation organic acids in the plant, on the processes of carbohydrate and nitrogen metabolism. By increasing the activity of enzymes involved in carbohydrate metabolism, potassium promotes the accumulation of starch in potato tubers, sugar in sugar beets and other plants; increases the resistance of plants to diseases, for example, grain breads - to powdery mildew and rust, vegetables, potatoes and root crops - to rot pathogens; in flax the yield and quality of fiber increases, in grain crops the sowing quality of seeds increases.
There is much more potassium in young parts and organs of the plant than in old ones, as well as in seeds, roots and tubers. For potassium deficiency in the nutrient medium, it flows from older organs and tissues to young growing organs, where it is reused (reutilized). In this case, the edges and tips of the leaves (primarily the lower ones) turn brown, take on a burnt appearance, and small rusty spots appear on the blade. With a lack of potassium, cells grow unevenly, which causes corrugation and dome-shaped curling of the leaves. Potatoes also develop a characteristic bronze coating on their leaves.
Potassium deficiency is especially common when cultivating potatoes, root crops, cabbage, silage crops and perennial herbs, which is associated with their high potassium consumption. Cereals are less sensitive to potassium deficiency. However, with an acute deficiency of potassium, they bush poorly, the internodes of the stems are shortened, and the leaves, especially the lower ones, wither even with sufficient moisture in the soil.
Calcium necessary for the normal growth of above-ground organs and plant roots. The need for it manifests itself even in the germination phase. With a lack of calcium and a sharp predominance of monovalent cations (H +, Na +, K +) or Mg 2+ cations in the soil solution, the physiological balance of the solution is disrupted. The growth and development of roots stops, they become thickened, do not form root hairs, their cell walls become slimy, darken and lose the ability to absorb nutrients. A deficiency of this element retards the growth of leaves, light yellow spots appear on them, then the leaves turn yellow and die prematurely. Calcium, unlike nitrogen, phosphorus and potassium, cannot be reused, so signs of calcium starvation appear primarily on young leaves.
Calcium enhances metabolism in plants, the movement of carbohydrates, the transformation of nitrogenous substances, accelerates the breakdown of reserve proteins of seeds during germination, plays an important role in the construction of normal cell membranes and the establishment of acid-base balance in plants.
Calcium enters plants throughout the entire period active growth. In the presence of nitrate nitrogen in the solution, its entry into plants increases, and in the presence of ammonia nitrogen, due to the antagonism between Ca 2+ and – cations, it decreases.
Plants vary greatly in their calcium intake. With a yield of 20 - 30 c/ha of grain, 200 - 300 c/ha of root crops and 500 - 700 c/ha of cabbage, rye, wheat, barley and oats yield from 20 to 40 kg of CaO, peas, vetch, beans, buckwheat, flax – 40 – 60, potatoes, lupine, corn, sugar beets – 60 – 120, clover, alfalfa – 120 – 250, cabbage – 300 – 500 kg.
Different parts and organs of the plant contain different amounts of calcium: there is much more of it in the leaves and stems than in the seeds. Therefore, most of the calcium removed from the soil through feed and bedding ends up in manure, i.e. returns to the fields.
Much more calcium is lost from the soil due to leaching. Its losses per season from the arable and subarable soil horizons in terms of CaO can reach 400–500 kg/ha. However, due to the fact that in the republic fairly high doses of lime fertilizers are used for liming and a significant amount of calcium comes with organic and phosphorus fertilizers, on average in the republic, 1 hectare contains up to 600 kg of calcium.
Magnesium is part of the chlorophyll molecule and is directly involved in photosynthesis. It is also contained in pectin substances and phytin, which accumulates mainly in seeds. For magnesium deficiency the chlorophyll content in the green parts of plants decreases, the leaves, especially the lower ones, become spotted - “marbled”, turn pale between the veins, and the green color remains along the veins (partial chlorosis). Then the leaves gradually turn yellow, curl at the edges and fall off prematurely. Plant development slows down and their growth deteriorates.
Magnesium, like phosphorus, is found mainly in growing parts and seeds. Unlike calcium, it is more mobile and can be redistributed by the plant: from old leaves to young ones, and after flowering, from leaves to seeds. Magnesium deficiency has a greater effect on the reproductive organs of plants (seeds, roots, tubers) than on the vegetative ones (straw, tops). This element plays an important role in various life processes: it participates in the movement of phosphorus in plants and carbohydrate metabolism, and affects the activity of redox processes.
The need of plants for magnesium is different: with 1 hectare of crops different cultures from 10 to 80 kg of MgO is carried out. The largest quantities are used by potatoes, sugar and fodder beets, leguminous crops, and legumes. Hemp, millet, buckwheat, and corn are sensitive to magnesium deficiency.
Soils contain less magnesium than calcium. Strongly podzolized acidic soils of light granulometric composition are especially poor in it, so the use of lime fertilizers containing magnesium on them significantly increases the yield.
Sulfur is important in plant life. The main amount of it is found in plant proteins (sulfur is part of the amino acids cysteine, cystine and methionine) and other organic compounds - enzymes, vitamins, mustard and garlic oils. Sulfur takes part in the nitrogen and carbohydrate metabolism of plants, in the process of respiration and fat synthesis. Plants from the legume and cabbage (cruciferous) families, as well as potatoes, contain more sulfur. With a lack of sulfur Small leaves with a light yellowish color are formed on elongated stems, and the growth and development of plants deteriorate.
Iron is part of the redox enzymes of plants and is involved in the synthesis of chlorophyll, respiration and metabolism. For iron deficiency due to disruption of chlorophyll formation in crops, especially fruit trees, chlorosis develops. The leaves lose their green color, then turn pale and fall off prematurely.
Bor plays an important role in plant life, it is necessary for the synthesis of carbohydrates, increases the formation of sugar in sugar beets, starch in potatoes, fiber in spinning crops, enhances the processes of flowering and fertilization.
More demanding on boron and are sensitive to its deficiency root vegetables, legumes, flax, potatoes and vegetables. In sugar, fodder and table beets, boron deficiency causes heart rot and the appearance of hollow roots. Flax with a lack of boron is affected by bacteriosis (calcium chlorosis), which sharply reduces the yield and quality of the fiber. With boron starvation of legumes, the development of root nodules is disrupted, symbiotic nitrogen fixation is reduced, and the growth and formation of reproductive organs slows down. Potatoes with a lack of boron are affected by scab, fruit trees develop dry tops, and external spotting and suberization of fruit tissues develop. Boron deficiency most often occurs on limed soddy-podzolic soils.
Molybdenum is part of the enzyme nitrate reductase, which is associated with the reduction of nitrates in plants. Legumes and vegetable crops, root crops, and rapeseed are especially demanding of the presence of molybdenum in the soil. External signs of molybdenum deficiency are similar to signs of nitrogen starvation: plant growth is sharply inhibited, they acquire a pale green color (leaf blades are deformed and leaves die prematurely).
Molybdenum deficiency limits the development of nodules on the roots of legumes and sharply reduces the yield and protein content in plants. A lack of molybdenum at large doses of nitrogen can lead to the accumulation in plants, especially vegetables and fodder, of increased amounts of nitrates, toxic to humans and animals. Molybdenum is also part of chloroplasts and is involved in the biosynthesis of nucleic acids, photosynthesis, respiration, the formation of pigments, vitamins, etc. Plants usually lack molybdenum by acidic soils, especially light granulometric composition.
Manganese is part of the redox enzymes involved in the processes of respiration, photosynthesis, carbohydrate and nitrogen metabolism in plants. It plays an important role in the absorption of nitrate and ammonium nitrogen by plants. The most demanding of its presence in accessible form in the soil are beets and other root vegetables, potatoes, cereals, cherries, apples and raspberries.
Characteristic symptom of manganese starvation– spot chlorosis of leaves. Small yellow chlorotic spots appear on the leaf blades between the veins, then the affected areas die. Manganese deficiency is most often observed on neutral and alkaline, as well as on light soils.
Copper It is also part of a number of redox enzymes and takes part in the processes of photosynthesis, carbohydrate and protein metabolism. Copper deficiency on drained peat soils it causes “till disease”, or “white plague”, in grain crops, which leads to whitening and drying of leaves. Affected plants do not form ears or panicles at all or partially, and the resulting inflorescences are sterile or poorly grained, which sharply reduces the grain yield, and in case of acute copper starvation, fruiting is completely absent.
Zinc has a multifaceted effect on the metabolism of energy and substances in plants, as it is part of enzymes and takes part in the synthesis of growth substances - auxins. If there is a shortage zinc inhibits plant growth, disrupts photosynthesis, the synthesis of carbohydrates and proteins, and the metabolism of phenolic compounds. Signs of zinc starvation: stunted growth of internodes, chlorosis and small leaves, rosette.
The most common people who suffer from zinc deficiency are fruit crops and flax on near-neutral and neutral soils with a high phosphorus content. With severe damage, fruit branches die, which leads to the appearance of “withered tops”. With a lack of zinc on calcareous soils, flax can be affected by bacteriosis, which sharply reduces the yield and quality of flax products.
Cobalt– an element necessary for plant and animal organisms. It is part of vitamin B 12. Cobalt enhances the activity of nodule bacteria and is part of many enzymes. With a lack of cobalt human metabolism is disrupted: the formation of hemoglobin, proteins, and nucleic acids decreases. When the cobalt content in feed is less than 0.07 mg/kg of dry matter, animals develop acobaltosis.
Soddy-podzolic soils of light granulometric composition are the poorest in cobalt. After liming, the need for cobalt increases. The content of 1.0 mg of cobalt in 1 kg of soil is considered low, medium – from 1.1 to 2.5, high – from 2.6 to 3.0 mg, excessive – more than 3.0 mg.
The relative content of nitrogen and ash elements in plants and their organs can vary widely, depending on biological features crops and varieties, age and nutritional conditions. The content of nitrogen and phosphorus is much higher in the economically valuable part of the crop - grain, roots and tubers - than in tops and straw, while there is more potassium in straw and tops (Table 2.3).
| Culture | N | P2O5 | K2O | MgO | CaO |
| Wheat: | |||||
| corn | 2,50 | 0,85 | 0,50 | 0,15 | 0,07 |
| straw | 0,50 | 0,20 | 0,90 | 0,10 | 0,18 |
| Peas (seeds) | 4,50 | 1,00 | 1,25 | 0,13 | 0,09 |
| Potatoes (tubers) | 0,32 | 0,14 | 0,60 | 0,06 | 0,08 |
| Linen: | |||||
| seeds | 4,00 | 1,35 | 1,00 | 0,47 | 0,27 |
| straw | 0,62 | 0,42 | 0,37 | 0,20 | 0,69 |
| Sugar beet (roots) | 0,24 | 0,08 | 0,25 | 0,05 | 0,06 |
| Cabbage (heads of cabbage) | 0,33 | 0,10 | 0,35 | 0,08 | 0,07 |
| Tomatoes (fruits) | 0,26 | 0,07 | 0,32 | 0,06 | 0,04 |
| Grasses (meadow hay) | 0,70 | 0,70 | 1,80 | 0,41 | 0,95 |
* For wheat, peas and grasses - % of dry matter, for other crops - % of wet weight.
To create a high yield, cabbage, potatoes, and sugar beets consume much more nutrients than grain crops.
The removal of nutrients from the soil by plants increases with increasing yield. However, a direct proportional relationship between these indicators is often not observed. With a higher yield level, the cost of nutrients per unit of production usually decreases.
In the grain crop, the ratio of N, P 2 O 5 and K 2 O fluctuates within relatively small limits and amounts to 2.5 - 3: 1: 1.8 - 2.6. On average, therefore, these crops consume 2.8 times more nitrogen and 2.2 times more potassium than phosphorus. Sugar beets, fodder root crops, potatoes and cabbage are characterized by a much higher consumption of potassium than nitrogen, and the ratio of N, P 2 O 5 and K 2 O can be 2.5 - 3.5: 1: 3.5 - 5.
The most productive use of nutrients from soil and fertilizers by plants is ensured under favorable soil and climatic conditions and a high level of agricultural technology. At the same time, the minimum consumption of nutrients per unit of yield of the main agricultural products is achieved. The average consumption of nitrogen, phosphorus and potassium for the formation of marketable products of the main agricultural crops is given in table. 2.4.
2.4. Average removal of nitrogen, phosphorus and potassium from 10 quintals of main and corresponding amount of by-products, kg
| Cultures | Product type | N | P2O5 | K2O |
| Winter wheat | Corn | |||
| Winter rye | » | |||
| Winter triticale | » | 11,5 | ||
| Barley | » | |||
| Oats | » | |||
| Buckwheat | » | |||
| Lupine | » | |||
| Peas | » | |||
| Fiber flax | Fiber | |||
| Sugar beet | Roots | 1,6 | 6,5 | |
| Fodder beet | » | 3,5 | 1,1 | 7,9 |
| Potato | Tubers | 5,4 | 1,6 | |
| Corn for silage | Green mass | 3,3 | 1,2 | 4,2 |
| Annual legume-cereal grasses | Hay | 17,4 | 5,4 | 25,9 |
| Perennial legumes and cereals | » | 17,3 | 5,4 | 25,7 |
| Perennial grasses | » | 14,9 | 4,5 | 24,1 |
| Perennial legumes | » | 21,4 | 5,1 | 22,2 |
| Cruciferous (average) | Green mass | 4,5 | 1,4 | 5,4 |
| Winter rapeseed | Seeds | |||
| Spring rape | » | |||
| Millet | Corn |
Having such data in relation to specific growing conditions, it is possible to calculate the required amount of nutrients to obtain the planned yield or their removal with the harvest. The latter depends on the biological characteristics of crops, their nutritional conditions, the chemical composition and structure of the crop.
QUESTIONS FOR SELF-CONTROL
2. What are the main functions of water in plant organisms?
3. Describe the content and composition of plant proteins in plants. What is "crude protein"?
4. List the main carbohydrates and indicate their content in plants.
5. Specify chemical composition vegetable oils and their content in major oilseeds.
6. What is the elemental chemical composition of plant dry matter?
7. What elements are called organogenic and why? What are macro-, micro- and ultra-microelements?
8. Name the main organic compounds that contain nitrogen, and indicate the signs of its deficiency in plants.
9. What role do phosphorus, potassium, calcium, magnesium, and sulfur play in plant physiology? Name the characteristic signs of their deficiency in plants.
10. List the main functions of microelements in plants and the characteristic signs of plant starvation due to a lack of individual microelements.
11. Based on data on the consumption of nitrogen, phosphorus and potassium per unit of harvest, calculate the amount of removal from 1 hectare of these elements with a grain crop yield at a yield of 20, 30, 40 and 50 c/ha and with a potato harvest at a yield of 100, 200, 300 c/ha.
Plant nutrition
Plant nutrition is the absorption and assimilation of nutrients from the environment. There are aerial and root nutrition of plants.
Air nutrition is assimilation green plant carbon dioxide from the air through the process of photosynthesis with the formation of organic substances with the participation of water and mineral compounds. Photosynthesis occurs in light with the help of chlorophyll contained in the leaves. During the light phase of photosynthesis, water decomposes, releasing oxygen, energy-rich compounds (ATP) and reduced products. From these compounds, in the next dark phase of photosynthesis, carbohydrates and other organic compounds are formed from CO 2.
When simple carbohydrates (hexoses) are formed as a product of photosynthesis, the overall equation of the process looks like this: 6CO 2 + 6H 2 O + 2874 kJ → C 6 H 12 O 6 + 6O 2. Through further transformations from simple carbohydrates in plants, more complex carbohydrates are formed, as well as other nitrogen-free organic compounds.
Amino acids, proteins and other organic nitrogen-containing substances in plants are synthesized from mineral compounds of nitrogen, phosphorus and sulfur and intermediate products of carbohydrate metabolism (synthesis and decomposition).
The intensity of photosynthesis and the accumulation of dry matter depend on lighting, the carbon dioxide content in the air, and the supply of plants with water and mineral nutrients.
Root nutrition- this is the absorption of water and mineral elements by the roots - nitrogen and ash elements in the form of ions (cations and anions), as well as small amounts of some organic compounds. Thus, nitrogen can be absorbed in the form of anions and cations, phosphorus and sulfur - in the form of anions of phosphoric and sulfuric acids H 2 PO 4 and, potassium, calcium, magnesium - in the form of cations K +, Ca 2+, Mg 2+, and microelements – in the form of corresponding cations or anions.
Plants absorb ions not only from the soil solution, but also ions absorbed by colloids. Moreover, plants are actively (due to the dissolving ability of root exudates, including carbonic acid, organic acids and amino acids) act on the solid phase of the soil, converting the necessary nutrients into an accessible form.
There is a close connection between aerial and root nutrition: some nutrients can enter the plant both from the soil and from the air. Thus, a small amount of carbon dioxide enters the roots from the soil, and sulfur, nitrogen, boron and other elements - from aqueous solutions, and with foliar feeding - through the leaves. For legumes, the main source of nitrogen is air.
The root system of plants and its absorption capacity. The root, first of all, is the organ that anchors the plant in the soil. Through it, water and nutrients dissolved in it enter the plant. The synthesis of organic substances, in particular amino acids, also occurs in the roots. The root systems of plants are developed differently and therefore have different absorption capacities. For example, the root system of flax is less developed compared to winter rye, and flax has a weaker ability to absorb nutrients from the soil.
Not the entire root system is capable of absorbing nutrients. As roots age (suberize), they lose this ability. The bulk of nutrients are absorbed by young growing areas of the root and root hairs. The larger the growing root surface, the more intensely nutrients enter the plant. The root system usually reaches its maximum development during the flowering phase of plants.
Mineral nutrition of plants
For the normal life cycle of a plant organism, a certain group of nutrients is necessary, the functions of which in the plant cannot be replaced by other chemical elements.
These are: 1) organogens – C (45% dry weight); O (42%); N (6.5%); N (1.5%) - in total 95%;
2) macroelements (1 – 0.01%): P, S, K, Ca, Mg, Fe, Al, Si, Cl, Na;
3) microelements (0.01 – 0.00001%): Mn, Cu, Zn, Co, Mo, B, I;
4) ultramicroelements (< 0,00001 %): Ag, Au, Pb, Ge….и др.
Yu. Liebig established that all of the listed elements are equivalent and the complete exclusion of any of them leads the plant to deep suffering and death; none of the listed elements can be replaced by another, even similar ones. chemical properties. Macroelements at a concentration of 200-300 mg/l in a nutrient solution do not yet have a harmful effect on the plant. Most microelements at a concentration of 0.1-0.5 mg/l inhibit plant growth.
For normal plant life there must be a certain ratio of various ions in the environment. Pure solutions of any one cation turn out to be toxic. Thus, when wheat seedlings were placed on pure solutions of KCL or CaCL 2, swellings first appeared on the roots, and then the roots died. Mixed solutions these salts did not have a toxic effect. The moderating effect of one cation on the action of another cation is called ion antagonism. Ion antagonism manifests itself both between different ions of the same valence, for example, between sodium and potassium ions, and between ions of different valence, for example, potassium and calcium. One of the reasons for the antagonism of ions is their effect on the hydration of cytoplasmic proteins. Divalent cations (calcium, magnesium) dehydrate colloids more strongly than monovalent cations (sodium, potassium). The next reason for the antagonism of ions is their competition for the active centers of enzymes. Thus, the activity of some respiratory enzymes is inhibited by sodium ions, but their effect is removed by the addition of potassium ions. In addition, ions may compete for binding to transporters during absorption. The action of one ion can enhance the influence of another ion. This phenomenon is called synergy. Thus, under the influence of phosphorus, the positive effect of molybdenum increases.
Physiological significance of micro- and macroelements
1. Contains biologically important nutrients;
2. Participate in the creation of a certain ionic concentration and stabilization of macromolecules;
3. Participate in catalytic reactions, being part of or activating individual enzymes.
Nitrogen (N 2)
It is part of proteins, nucleic acids, membrane phospholipids, porphyrins (the basis of chlorophyll and cytochromes), numerous enzymes (including NAD and NADP) and many vitamins.
With a lack of nitrogen in the environment, plant growth is inhibited, the formation of lateral shoots is weakened, small leaves and a pale green color of the leaves are observed due to the destruction of chlorophyll.
Despite the presence of 78% N 2 (410 5 t) in the atmospheric air, such molecular nitrogen is not absorbed higher plants(the nitrogen molecule (NN) is chemically inert; catalysts are required to break its three covalent bonds in the chemical process of ammonia synthesis, high temperature and pressure) and can be converted into a form accessible to them only due to the activity of nitrogen-fixing microorganisms. Of the lithospheric reserves of nitrogen (1810 15 tons), only its minimal part is concentrated in the soil, of which only 0.5 - 2% is directly available to plants: - these are NH 4 + and NO 3 - ions formed as a result of the mineralization of organic nitrogen of plant plants by bacteria and animal remains and humus. Namely, the processes:
1. Ammonification(conversion of organic nitrogen into NH 4 +);
2. Nitrification(oxidation of NH 4 + to NO 3 -);
3. Denitrification(anaerobic reduction of NO 3 - to N 2)
Fixation of molecular nitrogen ( N 2)
Chemical binding of molecular nitrogen in the form of NH 4 + or NO 3 - is carried out either as a result of electrical discharges in the atmosphere, or in the presence of a catalyst at a temperature of more than 500 0 C and an atmospheric pressure of about 35 MPa.
The biological binding of atmospheric molecular nitrogen is carried out by nitrogen-fixing microorganisms. They are:
1. Free living(Azotobacter, Beijrinckia - aerobic and Clostridium - anaerobic);
2. *Symbiotic(r. Rhizobium, which forms nodules on the roots of leguminous plants, and some actinomycetes).
*Infection of a host plant by symbiotic bacteria begins with the penetration of the bacterium into the root hair cell, migration into the cortex cells and intensive division of infected cells, which leads to the formation of nodules on the roots. In this case, the bacteria themselves turn into bacteroides, which are 40 times larger in size than the original bacterium. The main role in the process of nitrogen fixation belongs to the enzyme nitrogenase . The enzyme consists of two components: a higher molecular weight Fe-Mo protein (Mr = 200-250,000, 2 molecules of Mo, 30 molecules of Fe and 22 molecules of S) and Fe protein (Mr = 50-70,000, 4 molecules of Fe and 4 molecules S). Fe-Mo protein serves to bind and reduce molecular nitrogen, and Fe-protein serves as a source of electrons for the reduction of Fe-Mo protein, which it receives from ferredoxin. The entire complex works only in the presence of ATP hydrolysis and the protective effect of the leghemoglobin protein (synthesized by host cells and protects nitrogenase from oxygen).
The resulting NH 4 + binds to keto acids, forming amino acids transported into the cells of the host plant.
Nitrate reduction and ammonia assimilation pathways
Since only ammonium nitrogen is included in organic compounds, NO 3 - nitrate ions absorbed by the root must be reduced to ammonia in the cells. This is done in two stages:
1. Reduction of nitrate to nitrite, catalyzed by nitrate reductase (in the cytoplasm); NO 3 - ---2 e---- NO 2 -
2. Reduction of nitrite to ammonia, catalyzed by nitrite reductase (in chloroplasts). NO 2 - ---- 6e--- NH 4 +
Ammonia, formed during the reduction of nitrates or during the fixation of molecular nitrogen, is further absorbed by plants to form various amino acids. The primary acceptor of NH 4 + is α-ketoglutaric acid, which, under the influence glutamate dehydrogenase turns into glutamate.
For the growth and development of plants and vegetables, they need nutrients. The ratio of nutrients is different for species, varieties, growing period and age of the plant.
❖ Nitrogen is the main biogenic element for vegetable plants, which is part of protein and nucleic acids. Mineral forms of nitrogen entering the plant undergo a complex cycle of transformations, becoming included in the composition of organic acids. The process of nitrate reduction is catalyzed by enzymes and has several intermediate stages. The activity of reducing enzymes depends on magnesium and trace elements: molybdenum, copper, iron and manganese.
Nitrate nitrogen can accumulate in significant quantities, which is safe for plants, but nitrate content in vegetables above a certain level is harmful to humans.
Free ammonia is found in plants in small quantities. This is due to the fact that it quickly interacts with carbohydrates contained in plants. The result of the interaction is the formation of primary amino acids. Excessive accumulation of ammonia, especially with a deficiency of carbohydrates, leads to plant poisoning.
The quality of the product depends on which nitrogen compounds are absorbed in large quantities. With increased ammonia nutrition, the reducing ability of the plant cell increases and there is a predominant accumulation of reducing compounds. With nitrate nutrition, the oxidative ability of cell sap increases and more organic acids are formed.
The uptake of ammonia and nitrate nitrogen by plants depends on the concentration of the nutrient solution, its reaction, the content of accompanying elements, the supply of carbohydrates to plants and the biological characteristics of the crop.
❖ Phosphorus is found in plants in much smaller quantities than nitrogen. It acts as a nitrogen satellite; when it is deficient in plants, the accumulation of nitrate forms of nitrogen increases. The largest amount of phosphorus is concentrated in the reproductive organs: 3-6 times more than in the vegetative organs.
Phosphorus is contained in DNA and RNA nucleic acids, which are carriers of hereditary information. Phosphorus compounds with proteins (phosphoroproteins) are the most important plant enzymes. Phosphorus entering the plant promotes the accumulation of starch, sugars, coloring and aromatic substances, and increases the shelf life of fruits.
❖ Potassium regulates the water metabolism of plants, the physical state of cytoplasmic colloids, its swelling and viscosity. Under the influence of potassium, the water-holding capacity of protoplasm increases, which reduces the risk of short-term withering of plants due to lack of moisture. The presence of potassium in the plant cell ensures the normal course of oxidative processes, carbohydrate and nitrogen metabolism. The accumulation of potassium contributes to the activation of plant metabolic processes. Potassium helps improve immunity and enhances the use of ammonia nitrogen in the synthesis of amino acids and protein. Potassium is characterized by high mobility - outflow from older leaves to younger ones. In fact, the plant gets the opportunity to reuse potassium.
❖ Calcium plays an important role in photosynthesis, the movement of carbohydrates in the plant. It participates in the formation of cell membranes, determines water content and maintains the structure of cellular organelles. Lack of calcium affects the development of the root system, leaf growth slows down, and they die. Calcium deficiency manifests itself in young plants.
❖ Magnesium is part of the chlorophyll molecule and takes part in photosynthesis, and is also part of pectin substances and phytin. With a lack of magnesium, the chlorophyll content in the leaves decreases, and “marbling” appears. Magnesium and phosphorus are found in the growing parts of the plant. Magnesium accumulates in seeds. Magnesium is involved in the movement of phosphorus in plants. Activates enzymes. This element promotes the accumulation of essential oils and fats. With a lack of magnesium, oxidative processes increase, the activity of the peroxidase enzyme increases, and the content of invert sugar and ascorbic acid decreases
