What microelements are necessary for plant life. Why are microelements needed? Physical and chemical properties

What microelements are necessary for plant life. Why are microelements needed? Physical and chemical properties

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Optimizing plant nutrition and increasing the efficiency of fertilization are largely associated with ensuring an optimal ratio of macro- and microelements in the soil. Moreover, this is important not only for crop growth, but also for improving the quality of crop products. It should also be taken into account that new highly productive varieties have an intensive metabolism, requiring a full supply of all nutrients, including microelements.

The lack of microelements in the soil causes a decrease in the speed and consistency of the processes responsible for the development of the organism. Ultimately, the plants do not fully realize their potential and produce a low and not always high-quality harvest, and sometimes die.

The main role of microelements in increasing the quality and quantity of the crop is as follows:

1. In the presence of the required amount of microelements, plants have the ability to synthesize a full range of enzymes that allow more intensive use of energy, water and nutrition (N, P, K), and, accordingly, obtain a higher yield.

2. Microelements and enzymes based on them enhance the regenerative activity of tissues and prevent plant diseases.

4. Most trace elements are active catalysts that accelerate whole line biochemical reactions. The combined influence of microelements significantly enhances their catalytic properties. In some cases, only compositions of microelements can restore normal plant development.

Microelements have a great influence on biocolloids and influence the direction of biochemical processes.

According to the results of studies of the effectiveness of the use of microelements in agriculture clear conclusions can be drawn:

1. A lack of assimilable forms of microelements in the soil leads to a decrease in crop yields and a deterioration in product quality. It is the cause of various diseases (heart rot and hollowness of beets, cork spotting of apples, empty grain of cereals, rosette disease of fruits and various chlorotic diseases).

2. The simultaneous intake of macro- and microelements is optimal, especially for phosphorus and zinc, nitrate nitrogen and molybdenum.

3. During the entire growing season, plants experience a need for basic microelements, some of which are not reutilized, i.e. are not reused in plants.

4. Microelements in biologically active form currently have no equal in foliar feeding, which is especially effective when used simultaneously with macroelements.

5. Preventive doses of biologically active microelements, applied regardless of the soil composition, do not affect the total content of microelements in the soil, but have a beneficial effect on the condition of plants. When using them, the state of physiological depression in plants is eliminated, which leads to an increase in their resistance to various diseases, which will generally affect the increase in the quantity and quality of the crop.

6. It is especially necessary to note the positive effect of microelements on productivity, growth and development of plants, metabolism, provided they are introduced and strictly certain standards, and in the optimal time frame.

Agricultural crops have different needs for individual microelements. Agricultural plants according to their need for microelements are combined into the following groups (according to V.V. Tserling):

1. Plants with low removal of microelements and relatively high absorption capacity - cereals, corn, legumes, potatoes;

2. Plants with increased removal of microelements with low and medium absorption capacity - root crops (sugar, fodder, beets and carrots), vegetables, perennial herbs(legumes and cereals), sunflower;

3. Plants with high removal of microelements - agricultural crops grown under irrigation conditions against the background of high doses of mineral fertilizers.

Modern complex microfertilizers contain, in addition to a number of microelements, some meso- and macroelements. Let's consider the influence of individual macro-, meso- and microelements on agricultural plants.

Mesoelements

Magnesium

Magnesium is part of chlorophyll, phytin, pectin substances; found in plants and in mineral form. Chlorophyll contains 15-30% of all magnesium absorbed by plants. Magnesium plays an important physiological role during photosynthesis, affects redox processes in plants.

With a lack of magnesium, peroxidase activity increases, oxidation processes in plants intensify, and the content of ascorbic acid and invert sugar decreases. A lack of magnesium inhibits the synthesis of nitrogen-containing compounds, especially chlorophyll. An external sign of its deficiency is chlorosis of the leaves. In cereals, the leaves are marbling and banded; in dicotyledonous plants, the leaf areas between the veins turn yellow. Signs of magnesium starvation appear mainly on old leaves.

Magnesium deficiency manifests itself to a greater extent on sod-podzolic soils. acidic soils light granulometric composition.

Ammonia forms of nitrogen and potassium fertilizers impair the absorption of magnesium by plants, while nitrate forms, on the contrary, improve it.

Sulfur

Sulfur is part of all proteins, is found in amino acids, and plays important role in redox processes occurring in plants, in the activation of enzymes, in protein metabolism. It promotes the fixation of nitrogen from the atmosphere, enhancing the formation of nodules leguminous plants. The source of plant nutrition for sulfur is sulfuric acid salts.

With a lack of sulfur, protein synthesis is delayed, since the synthesis of amino acids containing this element is difficult. In this regard, the manifestations of signs of sulfur deficiency are similar to the signs of nitrogen starvation. Plant development slows down, leaf size decreases, stems lengthen, leaves and petioles become woody. During sulfur starvation, the leaves do not die, although the color becomes pale.

In many cases, when applying sulfur-containing fertilizers, increases in the yield of grain crops are noted.

Macronutrients

Potassium

Potassium affects the physicochemical properties of biocolloids (promotes their swelling) located in the protoplasm and walls of plant cells, thereby increasing the hydrophilicity of colloids - the plant retains water better and tolerates short-term droughts more easily. Potassium increases the entire course of metabolism, increases the vital activity of the plant, improves the flow of water into cells, increases osmotic pressure and turgor, and reduces evaporation processes. Potassium is involved in carbohydrate and protein metabolism. Under its influence, the formation of sugars in the leaves and its movement to other parts of the plant increases.

With potassium deficiency, protein synthesis is delayed and non-protein nitrogen accumulates. Potassium stimulates the process of photosynthesis and enhances the outflow of carbohydrates from the leaf blade to other organs.

Nitrogen

Nitrogen is part of such important organic substances as proteins, nucleic acids, nucleoproteins, chlorophyll, alkaloids, phosphates, etc.

Nucleic acids play a vital role in metabolism in plant organisms. Nitrogen is the most important component of chlorophyll, without which the process of photosynthesis cannot occur; is part of the enzymes that catalyze life processes in the plant organism.

In GLYCEROL preparations, nitrogen is in nitrate form. Nitrates are the best form of plant nutrition in at a young age when the leaf surface is small, as a result of which the process of photosynthesis is still weak in plants and carbohydrates and organic acids are not formed in sufficient quantities.

Microelements

Iron

The structural features of the iron atom, typical of transition elements, determine the variable valence of this metal (Fe 2+ /Fe 3+) and a pronounced ability to form complexes. These chemical properties determine the main functions of iron in plants.

Iron participates in redox reactions in both heme and non-heme forms.

Iron in organic compounds is necessary for redox processes that occur during respiration and photosynthesis. This is explained by the very high degree of catalytic properties of these compounds. Inorganic iron compounds are also capable of catalyzing many biochemical reactions, and in combination with organic substances, the catalytic properties of iron increase many times.

The iron atom is oxidized and reduced relatively easily, which is why iron compounds are carriers of electrons in biochemical processes. These processes are carried out by enzymes containing iron. Iron also has a special function - its indispensable participation in the biosynthesis of chlorophyll. Therefore, any reason that limits the availability of iron for plants leads to severe diseases, in particular chlorosis.

With a lack of iron, plant leaves become light yellow, and when starved, they become completely white (chlorotic). Most often, chlorosis as a disease is characteristic of young leaves. With acute iron deficiency, plant death occurs. In trees and shrubs, the green color of the apical leaves disappears completely, they become almost white and gradually dry out. Iron deficiency for plants is most often observed on carbonate and poorly drained soils.

In most cases, microelements in a plant are not reutilized if there is a deficiency of any of them. It has been established that on saline soils, the use of microelements enhances the absorption of nutrients from the soil by plants, reduces the absorption of chlorine, while the accumulation of sugars and ascorbic acid increases, a slight increase in chlorophyll content is observed, and the productivity of photosynthesis increases.

Iron deficiency most often occurs on carbonate soils, as well as on soils with a high content of digestible phosphates, which is explained by the conversion of iron into inaccessible compounds.

Soddy-podzolic soils are characterized by an excess amount of iron.

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 education and development reproductive organs, destruction of vascular tissue, etc. Lack of boron very often causes destruction of young growing tissues.

Under the influence of boron, the synthesis and movement of carbohydrates, especially sucrose, from leaves to fruiting organs and roots are improved. It is known that monocotyledonous plants are less demanding of boron than dicotyledonous plants.

There is evidence in the literature that boron improves the movement of growth substances and ascorbic acid from leaves to fruiting organs. It also promotes better use of calcium in metabolic processes in plants. Therefore, with a lack of boron, plants cannot normally use calcium, although the latter is found in sufficient quantities in the soil. It has been established that the amount of boron absorption and accumulation by plants increases with increasing potassium content in the soil.

A lack of boron leads not only to a decrease in crop yield, but also to a deterioration in its quality. It is known that many functional diseases of cultivated plants are caused by insufficient amounts of boron. For example, on calcareous sod-podzolic and sod-gley soils, flax bacteriosis is observed. In beets, chlorosis of the core leaves and root rot (dry rot) appear.

It should be noted that boron is necessary for plants throughout the growing season. The exclusion of boron from the nutrient medium at any phase of plant growth leads to its disease.

Many studies have found that flowers are the richest in boron compared to other parts of plants. It plays an essential role in fertilization processes. If it is excluded from the nutrient medium, plant pollen germinates poorly or even not at all. In these cases, the addition of boron promotes better germination of pollen, eliminates the abscission of ovaries and enhances the development of reproductive organs.

Boron plays an important role in cell division and protein synthesis and is an essential component of the cell membrane. Boron plays an extremely important function in carbohydrate metabolism. Its deficiency in the nutrient medium causes the accumulation of sugars in plant leaves. This phenomenon is observed in crops that are most responsive to boron fertilizers.

With a lack of boron in the nutrient medium, there is also a violation anatomical structure plants, such as poor xylem development, fragmentation of the phloem of the main parenchyma and degeneration of the cambium. The root system develops poorly, since boron plays a significant role in its development. Sugar beets are especially in need of boron.

Boron is also important for the development of nodules on the roots of legumes. If there is insufficiency or absence of boron in the nutrient medium, the nodules develop poorly or do not develop at all.

Copper

The role of copper in plant life is very specific: copper cannot be replaced by any other element or their sum.

A sign of copper deficiency in plants appears as “handling disease.” In cereals, symptoms appear as
whitening and drying of the tops of young leaves. The whole plant becomes light green in color and heading is delayed. With severe copper starvation, the stems dry out. Such plants do not produce a harvest at all, or the yield is very low and Bad quality. Sometimes, during severe copper starvation, the plants bush abundantly and often continue to form new shoots after the tops have completely dried out. Strong and extended tillering of barley during copper starvation favors its damage by the Swedish fly.

Different crops have different sensitivities to copper deficiency. Plants can be ranked in the following order in order of decreasing responsiveness to copper: wheat, barley, oats, corn, carrots, beets, onions, spinach, alfalfa and White cabbage. Potatoes, tomatoes, red clover, beans, and soy are characterized by average responsiveness. Varietal features plants within the same species are of great importance and significantly influence the degree of manifestation of symptoms of copper deficiency.

Copper deficiency often coincides with zinc deficiency, and in sandy soils also with magnesium deficiency. The application of high doses of nitrogen fertilizers increases the need of plants for copper and contributes to the exacerbation of symptoms of copper deficiency. This indicates that copper plays an important role in nitrogen metabolism.

Copper is involved in carbohydrate and protein metabolism in plants. Under the influence of copper, both peroxidase activity and the synthesis of proteins, carbohydrates and fats increase. A lack of copper causes a decrease in the activity of synthetic processes in plants and leads to the accumulation of soluble carbohydrates, amino acids and other breakdown products of complex organic substances.

When feeding on nitrates, copper deficiency inhibits the formation of early products of their reduction and initially does not affect the enrichment of amino acids, amides, proteins, peptones and polypeptides with nitrogen. Subsequently, a strong inhibition of the enrichment of 15 N in all fractions of organic nitrogen is observed, and it is especially significant in amides. When fed with ammonia nitrogen, the lack of copper delays the incorporation of heavy nitrogen into protein, peptones and peptides already in the first hours after applying nitrogen fertilizing. This indicates a particularly important role for copper in the use of ammonia nitrogen.

In corn, copper increases the content of soluble sugars, ascorbic acid and, in most cases, chlorophyll, enhancing the activity of the copper-containing enzyme polyphenoloxidase and reducing the activity of peroxidase in corn leaves. It also increases the protein nitrogen content in the leaves of ripening corn.

Copper plays an important role in photosynthesis processes. With its deficiency, the destruction of chlorophyll occurs much faster than with a normal level of plant nutrition with copper.

Thus, copper affects the formation of chlorophyll and prevents its destruction.

In general, it should be said that the physiological and biochemical role of copper is diverse. Copper affects not only the carbohydrate and protein metabolism of plants, but also increases the intensity of respiration. The participation of copper in redox reactions is especially important. In plant cells, these reactions occur with the participation of enzymes that contain copper. Therefore, copper is an integral part of a number of important oxidative enzymes - polyphenol oxidase, ascorbate 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 divalent to monovalent state and back).

A characteristic feature of the action of copper is that this microelement increases the resistance of plants against fungal and bacterial diseases. Copper reduces diseases of grain crops by various types of smut and increases the resistance of tomatoes to brown spot.

Zinc

All cultivated plants in relation to zinc are divided into 3 groups: very sensitive, moderately sensitive and insensitive. The group of very sensitive crops includes corn, flax, hops, grapes, fruits; moderately sensitive are soybeans, beans, forage legumes, peas, sugar beets, sunflowers, clover, onions, potatoes, cabbage, cucumbers, berries; mildly sensitive - oats, wheat, barley, rye, carrots, rice, alfalfa.

Zinc deficiency for plants is most often observed in sandy and carbonate soils. There is little available zinc in peatlands and also in some marginal soils.

Zinc deficiency usually causes stunted plant growth and a decrease in the amount of chlorophyll in leaves. Signs of zinc deficiency are most common in corn.

Zinc deficiency has a stronger effect on the formation of seeds than on the development of vegetative organs. Symptoms of zinc deficiency are widespread in various fruit crops (apple, cherry, apricot, lemon, grapes). Citrus crops are particularly affected by zinc deficiency.

The physiological role of zinc in plants is very diverse. It has a great influence on redox processes, the speed of which is noticeably reduced when it is deficient. Zinc deficiency leads to disruption of carbohydrate conversion processes. It has been established that with a lack of zinc, phenolic compounds, phytosterols or lecithins accumulate in the leaves and roots of tomato, citrus fruits and other crops. Some authors consider these compounds as products of incomplete oxidation of carbohydrates and proteins and see this as a violation of redox processes in the cell. With a lack of zinc, reducing sugars accumulate in tomato and citrus plants and the starch content decreases. There is evidence that zinc deficiency is more pronounced in plants rich in carbohydrates.

Zinc is involved in the activation of a number of enzymes associated with the respiration process. The first enzyme in which zinc was discovered was carbonic anhydrase. Carbonic anhydrase contains 0.33-0.34% zinc. It determines the different intensity of the processes of respiration and CO 2 release by animal organisms. The activity of carbonic anhydrase in plants is much weaker than in animals.

Zinc is also included in other enzymes - triosephosphate dehydrogenase, peroxidase, catalase, oxidase, polyphenol oxidase, etc.

It was found that large doses of phosphorus and nitrogen increase signs of zinc deficiency in plants. In experiments with flax and
other crops have found that zinc fertilizers are especially necessary when applying high doses of phosphorus.

Many researchers have proven the connection between the supply of zinc to plants and the formation and content of auxins in them. Zinc starvation is caused by the absence of active auxin in plant stems and its reduced activity in leaves.

The importance of zinc for plant growth is closely related to its participation in nitrogen metabolism

The importance of zinc for plant growth is closely related to its participation in nitrogen metabolism. Zinc deficiency leads to a significant accumulation of soluble nitrogen compounds - amides and amino acids, which disrupts protein synthesis. Many studies have 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 increases. The use of zinc fertilizers increases the content of ascorbic acid, dry matter and chlorophyll in corn leaves. Zinc fertilizers increase the drought, heat and cold resistance of plants.

Manganese

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. With a lack of manganese, excess iron accumulates in plants, which causes chlorosis. Excess manganese delays the flow of iron into the plant, which also results in chlorosis, but this time from a lack of iron. The accumulation of manganese in concentrations toxic to plants is observed on acidic soddy-podzolic soils. The toxicity of manganese is eliminated by molybdenum.

According to numerous studies, the presence of antagonism between manganese and calcium, manganese and cobalt has been revealed; There is no antagonism between manganese and potassium.

On sandy soils, nitrates and sulfates reduce the mobility of manganese, but sulfates and chlorides do not have a noticeable effect.
render. When liming soils, manganese transforms into forms that are inaccessible to plants. Therefore, by liming it is possible to eliminate the toxic effect of this element on some podzolic (acidic) soils of the non-chernozemic zone.

The share of manganese in the primary products of photosynthesis is 0.01–0.03%. An increase in the intensity of photosynthesis under the influence of manganese, in turn, has an effect on other life processes of plants: the content of sugars and chlorophyll in plants increases and the intensity of respiration and fruiting of plants increases.

The role of manganese in plant metabolism is similar to the functions of magnesium and iron. Manganese activates numerous enzymes, especially when phosphorylated. Due to its ability to transfer electrons by changing valence, it participates in various redox reactions. In the light reaction of photosynthesis, it participates in the splitting of water molecules.

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 on carbonate, heavily limed, as well as on some peaty and other soils with a pH above 6.5.

Manganese deficiency becomes noticeable first on young leaves by a lighter green color or discoloration (chlorosis). In contrast to glandular chlorosis, in monocots, gray, gray-green or brown, gradually merging spots appear in the lower part of the leaf blade, often with a darker border. The 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. In addition, brown necrotic spots appear very soon. Leaves die even faster than with iron deficiency.

Manganese is involved not only in photosynthesis, but also in the synthesis of vitamin C. With a lack of manganese, the synthesis of organic substances decreases, the chlorophyll content in plants decreases, and they develop chlorosis. External symptoms of manganese starvation: gray leaf spot in cereals; chlorosis in sugar beets, legumes, tobacco and cotton; In fruit and berry plantings, a lack of manganese causes yellowing of the edges of leaves and drying out of young branches.

Manganese deficiency in plants worsens at low temperatures and high humidity. In this regard, winter grains are most sensitive to its deficiency in early spring. With a lack of manganese, excess iron accumulates in plants, which causes chlorosis. Excess manganese delays the flow of iron into the plant, which also results in chlorosis, but this time from a lack of iron. The accumulation of manganese in concentrations toxic to plants is observed on acidic soddy-podzolic soils. The toxicity of manganese is eliminated by molybdenum.

On sandy soils, nitrates and sulfates reduce the mobility of manganese, but sulfates and chlorides do not have a noticeable effect. When liming soils, manganese transforms into forms that are inaccessible to plants. Therefore, by liming it is possible to eliminate the toxic effect of this element on some podzolic (acidic) soils of the non-chernozemic zone.

An increase in the intensity of photosynthesis under the influence of manganese, in turn, has an effect on other life processes of plants: the content of sugars and chlorophyll in plants increases and the intensity of respiration and fruiting of plants increases.

Silicon

For most higher plants Silicon (Si) is a useful chemical element. It helps to increase the mechanical strength of leaves and plant resistance to fungal diseases. In the presence of silicon, plants better tolerate unfavorable conditions: moisture deficiency, imbalance of nutrients, toxicity heavy metals, soil salinization, exposure to extreme temperatures.

According to researchers, the use of silicon increases the resistance of plants to moisture deficiency. Plants can absorb silicon through leaves when foliar feeding with microfertilizers. In plants, silicon is deposited mainly in epidermal cells, forming a double cuticular-silicon layer (primarily on leaves and roots), as well as xylem cells. Its excess is transformed into different kinds phytoliths.

Thickening of the walls of epidermal cells due to the accumulation of silicic acid in them and the formation of a silicon-cellulose membrane contributes to more economical consumption of moisture. When monosilicic acids absorbed by the plant are polymerized, water is released, which is used by the plants. On the other hand, the positive effect of silicon on the development of the root system and an increase in its biomass helps to improve water absorption by the plant. This contributes to the provision of plant tissues with water under conditions of water deficiency, which in turn affects the physiological and biochemical processes occurring in them.

The direction and intensity of these processes is largely determined by the balance of endogenous phytohormones, which are one of the leading factors in the regulation of plant growth and development.

Many effects caused by silicon are explained by its modifying effect on the sorption properties of cells (cell walls), where it can accumulate in the form of amorphous silica and bind with various organic compounds: lipids, proteins, carbohydrates, organic acids, lignin, polysaccharides. An increase in the sorption of manganese by cell walls and, as a consequence, plant resistance to its excess in the environment was recorded in the presence of silicon. A similar mechanism underlies the positive effect of silicon on plants under conditions of excess aluminum ions, which is eliminated by the formation of Al-Si complexes. In the form of silicates, it is possible to immobilize excess zinc ions in the cytoplasm of a plant cell, which was established using the example of zinc that is resistant to elevated concentrations. In the presence of silicon, the negative effect of cadmium on plants is weakened due to the limitation of the transport of cadmium into the shoots. In saline soil conditions, silicon can prevent the accumulation of sodium in shoots.

Obviously, with excess content in the environment of many chemical elements silicon is good for plants. Its connections
are capable of adsorbing ions of toxic elements, limiting their mobility both in the environment and in plant tissues. The effect of silicon on plants with a lack of chemical elements, especially necessary for small quantity, for example, microelements, have not yet been studied.

In the conducted studies, it was established that the effect of silicon on the concentration of pigments (chlorophyll a, b carotenoids) in leaves appears with a lack of iron and is dual in its direction. Evidence of inhibition in the presence of silicon of the development of chlorosis has been revealed, which is observed exclusively in young dicotyledonous plants.

According to research results, cells of Si-treated plants are able to bind iron with a strength sufficient to limit its movement throughout the plant.

Silicon compounds increase the economically valuable part of the crop with a tendency to reduce straw biomass. At the beginning of the growing season, in the tillering phase, the influence of silicon on the growth of vegetative mass is significant and averages 14-26%.

Treatment of seeds with silicon compounds has a great influence on the phosphorus content of the grain and increases the weight of 1000 grains.

Sodium

Sodium is one of the potential-forming elements necessary to maintain specific electrochemical potentials and osmotic functions of the cell. Sodium ion ensures optimal conformation of enzyme proteins (enzyme activation), forms bridging bonds, balancing anions, controls membrane permeability and electrical potentials.

Nonspecific functions of sodium are associated with the regulation of osmotic potential.

Sodium deficiency occurs only in sodium-loving plants, such as sugar beets, chard and turnips. A lack of sodium in these plants leads to chlorosis and necrosis, the leaves of the plants become dark green and dull, quickly wither during drought and grow in a horizontal direction, brown spots in the form of burns may appear on the edges of the leaves.

General ideas about mineral nutrition.

Plants feed on simple substances not only from the air (carbon dioxide and water - photosynthesis), but also from the soil (ions of mineral salts - mineral nutrition). They assimilate simple inorganic compounds from external nature, synthesize complex organic substances from them and build their body.

Organic plant matter consists of organogenic elements: carbon - 45%, oxygen - 42%, hydrogen - 6.5% and nitrogen - 2.5% - a total of 95%. Carbon, hydrogen, and oxygen are absorbed by plants as a result of air nutrition. Plants also contain 5-10% ash mineral elements– they remain after burning plants.

The process of assimilation of ash elements and nitrogen from the soil is called soil or mineral nutrition of plants. Supplying plants with a complete set of mineral elements in an optimal ratio is important for plant metabolism, normal development, and overcoming adverse environmental influences. Agriculture has long learned to regulate the mineral nutrition of plants using agricultural practices and the application of mineral fertilizers.

Macro- and microelements necessary for plants and their physiological role.

Analysis detects almost all elements in plants periodic table Mendeleev. The main ones are micro- and macroelements.

macronutrients

microelements

1.Macroelements.

Nitrogen.

It is part of proteins, nucleic acids, ATP, ADP, coenzymes, chlorophylls, cytochromes, some lipids, many vitamins, plant growth hormones. Nitrogen is an integral part of substances essential for life. It directly affects plant growth.

Phosphorus.

It is part of DNA, RNA, ATP, coenzymes, phospholipids, sugar phosphates, proteins, and many other metabolic intermediate products. Phosphorus-containing substances occupy a central place in constructive and energy metabolism. The role of phosphorus in photosynthesis and respiration is important. In addition, energy during photosynthetic and oxidative phosphorylation is stored in high-energy phosphate bonds of ATP. Phosphorus is important for flowering and fruiting of plants.

Potassium.

It is not part of organic matter, regulates the state of the cytoplasm of plant cells, increasing its permeability and reducing viscosity, is found in cell sap, takes Active participation in the osmotic phenomena of cells, the movement of stomata, enhances the biosynthesis of starch, accelerates the processes of photosynthetic phosphorylation, and the outflow of assimilates. The main role of potassium is regulatory – it takes part in metabolic processes in the plant.

Sulfur.

Contained in all proteins, part of amino acids (methionine, cysteine, cystine), vitamins (thiamine, biotin), lipoic acid, sulfolipids, coenzyme A, garlic and mustard oils. Disulfide groups are involved in the formation of the tertiary structure of proteins, and sulfhydryl groups are involved in the formation of enzymes involving NAD and FAD. Sulfur plays an important role in protein and lipid metabolism, in plant energy, and is important for maintaining the structure of chloroplast thylakoid membranes.

Calcium.

Contained in plants in organic substances and in ionic form, it is part of the plant cell wall, chromosomes, membranes, stabilizing their structure. In its free form, it acts as a potassium antagonist - it increases viscosity and reduces the permeability of the cytoplasm, neutralizes excess organic acids in cells, and supports the vital activity of meristems.

Magnesium.

Found in the chlorophyll molecule and chelates, it plays a role in stabilizing the structure of ribosomes, regulates the state of the cytoplasm, increasing viscosity and decreasing the permeability of the cytoplasm, and is a cofactor for many enzymes.

Sodium.

For some groups of plants (halophytes), saline habitats are important. Not needed for most plants.

Silicon.

IN large quantities found in the leaves of some tree species (in spruce needles), is part of the cell walls of wood, and the shell of diatoms. Many plants do without it.

2.Microelements.

Iron.

Contained in an amount of 0.08%. As a cofactor, it is part of the enzymes involved in the synthesis of chlorophyll, it is part of oxyreductases, in the nitrogenase enzyme complex, that is, it is involved in nitrogen fixation, it is contained in cytochrome molecules, ferredoxin, and is involved in the process of electron transfer.

Copper.

It is found in the composition of enzymes involved in the biosynthesis of chlorophyll, is part of the oxidase enzymes involved in respiration, is part of the plastocyanin protein, activates nitroreductase, that is, participates in nitrogen metabolism. Lack of copper causes stunted growth and flowering.

Zinc.

Plays an important role in protein metabolism, being part of peptidohydrolases, takes part in the synthesis of indolylacetic acid (plant hormone), affects the synthesis of the amino acid tryptophan, activates a number of glycolysis enzymes and PPP reactions.

Has a wide spectrum of action. It influences cell division, promoting the growth of root and above-ground parts of plants, participates in pollen germination and ovary growth, promotes the outflow of carbohydrates from chloroplasts, increases the elasticity of the cell wall and drought resistance of plants.

Manganese.

As a cofactor of some enzymes, it catalyzes the reactions of photosynthesis and respiration, participates in the process of nitrate reduction, iron metabolism, maintains the structure of thylakoid membranes, activates Krebs cycle enzymes, and participates in the synthesis of m-RNA in the nucleus.

Molybdenum.

Plays an important role in nitrogen metabolism, participates in the process of nitrogen fixation, in the reactions of protein biosynthesis, ascorbic acid, promotes better absorption of calcium, and the growth of plant root systems. With a lack of molybdenum, plant growth is inhibited .

In addition to the listed microelements, selenium, iodine, vanadium, titanium, and nickel play an important role in plant metabolism.

Students, graduate students, young scientists who use the knowledge base in their studies and work will be very grateful to you.

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The role of macroelements in the plant

Introduction

In a plant organism, all processes are closely interconnected. The exclusion of any essential element from the nutrient medium quickly causes changes in many, if not all, metabolic processes.

In general, we can say that nutritional elements have the following meaning:

1) are part of biologically important organic substances;

2) participate in the creation of a certain ionic concentration, stabilization of macromolecules and colloidal particles (electrochemical role);

3) participate in catalytic reactions, being part of or activating individual enzymes. In many cases, the same element can play different roles. Some elements perform all three functions. Plants are capable of absorbing almost all elements of the periodic table from the environment in larger or smaller quantities. But for the normal life cycle of a plant organism, only a certain group of basic nutrients is necessary. Elements such as carbon, hydrogen and oxygen are obtained by plant organisms from air and water, and the rest from the soil.

In the dry mass of plant tissues, carbon and oxygen account for an average of 45% each, hydrogen - 6, nitrogen - 1.5%. Depending on their content in tissues, mineral elements are divided into macro- and microelements. Macroelements include: nitrogen, potassium, calcium, magnesium, phosphorus, sulfur, iron. Their content in plant tissues calculated on a dry weight basis varies from 0.1 to 1.5%.

1. Role athota, potassium and phosphorus in the plant

Nitrogen is part of amino acids, amides, proteins, nucleic acids, nucleotides and many other vital organic compounds. For plants, nitrogen is the most deficient nutrient. Therefore, in metabolism, nitrogen is used by plants very sparingly and nitrogen compounds are never released by them as waste products and, where possible, are replaced with nitrogen-free compounds.

With a lack of nitrogen, plant growth is inhibited, the formation of lateral shoots and tillering in cereals is weakened, and small leaves are observed. At the same time, root branching decreases, but the ratio of the mass of the root system to the above-ground part may increase. One of the early manifestations of nitrogen deficiency is a pale green color of leaves caused by weakened chlorophyll synthesis. Without nitrogen, protein substances cannot be sensitized, and without them the protoplast of a living cell cannot be formed. Prolonged nitrogen starvation leads to the hydrolysis of proteins and the destruction of chlorophyll in the lower leaves and the outflow of the resulting nitrogen compounds to young tissues. Moreover, depending on the type of plant, the color of the lower leaves acquires yellow, orange or red tones. With more severe nitrogen starvation, necrosis appears, tissues dry out and die. Nitrogen deficiency leads to a shorter period of vegetative growth and earlier seed ripening.

Plant roots are able to absorb nitrogen from the soil in the form of anion and cation. The main forms of nitrogen on Earth are tightly bound nitrogen of the lithosphere and molecular nitrogen (N 2) of the atmosphere. Molecular nitrogen is not directly absorbed by plants and is converted into an accessible form only through the activity of nitrogen-fixing microorganisms.

The phosphorus content of plants is about 0.2% on a dry weight basis. Phosphorus enters root system and functions in the plant in the form of oxidized compounds, mainly orthophosphoric acid residues (H 2 PO 4-,). The physiological significance of phosphorus is determined by the fact that it is part of a number of organic compounds, such as nucleic acids (DNA and RNA), nucleotides (ATP, NAD, NADP), nucleoproteins, vitamins and many others, which play a central role in metabolism. Phosphorus plays a particularly important role in the energy of the cell, since it is in the form of high-energy ester bonds of phosphorus or pyrophosphate bonds in nucleoside di-, nucleoside triphosphates and polyphosphates that energy is stored in a living cell. Phospholipids are components of biological membranes, and it is the presence of phosphate in their structure that ensures hydrophilicity, the rest of the molecule is lipophilic. Many vitamins and their derivatives containing phosphorus are coenzymes and are directly involved in catalytic reactions that accelerate the course of the most important processes metabolism (photosynthesis, respiration, etc.). Phosphorus is contained in such an organic compound as phytin (Ca-Mg salt of inositol phosphoric acid), which is the main reserve form of phosphorus in the plant. There is especially a lot of phytin in the seeds (0.5 - 2% by dry weight). During all transformations in the plant organism, phosphorus retains its oxidation state. In fact, all transformations are reduced only to the addition or transfer of a phosphoric acid residue (phosphorylation and transphosphorylation).

Another unique function of phosphorus is its participation in the phosphorylation of cellular proteins using protein kinases. This mechanism controls many metabolic processes, since the inclusion of phosphate in a protein molecule leads to a redistribution of electrical charges in it and, as a result, to a modification of its structure and function. Protein phosphorylation regulates processes such as RNA and protein synthesis, cell division, cell differentiation and many others.

Phosphorus, like nitrogen, is easily redistributed between plant organs, flowing from aging leaves to young ones, into growth cones and developing fruits.

An external symptom of phosphorus starvation is a bluish-green color of the leaves, often with a purple or bronze tint, which is associated with inhibition of protein synthesis and the accumulation of sugars. At the same time, the leaves become small and narrower, the growth of cells and tissues stops, and the transition to the reproductive phase of plant development is delayed.

With phosphorus deficiency, the rate of oxygen absorption decreases, the activity of enzymes involved in respiratory metabolism changes, and some non-mitochondrial oxidation systems (glycolic acid oxidase, ascorbate oxidase) begin to work more actively. Under conditions of phosphorus starvation, the processes of decomposition of organophosphorus compounds and polysaccharides are activated, and the synthesis of proteins and free nucleotides is inhibited.

Potassium is one of the most essential elements mineral nutrition plants. Its content in tissues averages 0.5 - 1.2% based on dry weight. The concentration of potassium in the cell is 100-1000 times higher than its content in external environment. Therefore, in the membranes of cells in contact with the soil solution, a powerful system of ion pumps functions, ensuring the accumulation of K + ions inside the plant organism.

The potassium content in the soil is 5-50 times greater than the phosphorus and nitrogen reserves. In the soil it is found in minerals, in colloidal particles (exchangeable and non-exchangeable state) and in mineral salts of the soil solution accessible to plants. As available forms of potassium are consumed, its reserves are replenished by the exchange pool of this cation, and when the latter decreases, due to various forms of bound potassium. Alternate drying and moistening of the soil, the activity of the root system and microflora contribute to the transition of potassium into forms accessible to the plant.

The physiological role of potassium cannot be considered fully understood. Potassium is not included in any organic compound. Most of it (about 80%) in the cell is in free ionic form and is easily removed cold water, and about 20% is in the adsorbed state. Potassium reduces the viscosity of protoplasm, increases its hydration, increasing the hydration of proteins. Potassium salts are soluble and participate in the regulation of the osmotic potential of the cell. In particular, K+ is of great importance in the regulation of stomatal function. It has been shown that the opening of stomata in the light is associated with the accumulation of potassium ions in the guard cells. In this case, K + in exchange for H + comes from the cells surrounding the stomata. Root pressure also largely depends on the presence of K + in the sap.

A small part of potassium (about 1%) is tightly bound to the proteins of mitochondria and chloroplasts and stabilizes the structure of these organelles. Potassium deficiency disrupts the lamellar-granular structure of chloroplasts and mitochondrial membranes. Potassium activates the work of many enzyme systems. More than 60 enzymes are known that require the presence of K + ions to function. It is necessary in the processes of incorporating phosphate into organic compounds, for the synthesis of proteins, polysaccharides and many other reactions. Potassium also activates a number of Krebs cycle enzymes. Potassium deficiency slows down the transport of sucrose through the phloem. The influence of K+ on carbohydrate transport determines its role in crop formation. Under the influence of potassium, the accumulation of starch, sucrose, and monosaccharides increases.

With a lack of potassium, the leaves begin to turn yellow at the edges, then their edges and tops acquire a brown color, sometimes with red “rusty” spots and look as if burned, but at the final stage of potassium starvation, these areas die off. Potassium deficiency inhibits the process of cell division and elongation, which leads to the formation of rosette forms of plants. Potassium starvation also reduces the intensity of photosynthetic processes, primarily by reducing the rate of outflow of assimilates.

In a plant, potassium is concentrated in growing tissues with intense metabolism - meristems, cambium, young leaves, shoots, buds. In the cell, it makes up the bulk of cations, about 80% of it is concentrated in the vacuole. Potassium is mainly in ionic form, has a very high mobility and is well reutilized.

2. Calcium, magnesium and sulfur in plant organisms

chlorophyllmineral plant

In relation to calcium, plants are divided into three groups: calciumphiles, calciumphobes and neutral species. The calcium content in plants is 0.5 - 1.5% of the dry matter weight, but in mature tissues of calciophilic plants it can reach 10%. The above-ground parts accumulate more calcium per unit mass than the roots.

The chemical properties of calcium are such that it easily forms fairly strong and at the same time labile complexes with oxygen compounds of macromolecules. Calcium can bind intramolecular sites of proteins, leading to changes in conformation, and form bridges between complex compounds of lipids and proteins in the membrane or pectin compounds in the cell wall, ensuring the stability of these structures. Therefore, accordingly, with calcium deficiency, membrane fluidity sharply increases, the processes of membrane transport and bioelectrogenesis are also disrupted, cell division and elongation are inhibited, and root formation processes stop. Lack of calcium leads to swelling of pectin substances and disruption of the structure of cell walls. Necrosis appears on the fruits. At the same time, the leaf blades become bent and twisted, the tips and edges of the leaves initially turn white and then turn black. Roots, leaves and individual sections of the stem rot and die. The lack of calcium primarily affects young meristematic tissues and the root system.

Ca 2+ ions play an important role in regulating the uptake of ions by plant cells. The excess content of many cations toxic to the plant (aluminum, manganese, iron, etc.) can be neutralized by binding to the cell wall and displacing Ca 2+ ions from it into the solution.

Calcium is important in cell signaling processes as a secondary messenger. Ca 2+ ions have the universal ability to conduct a wide variety of signals that have a primary effect on the cell - hormones, pathogens, light, gravitational and stress influences. The peculiarity of the transmission of information in the cell using Ca 2+ ions is the wave method of signal transmission. Ca waves and Ca oscillations, initiated in certain areas of cells, are the basis of calcium signaling in plant organisms.

The cytoskeleton is very sensitive to changes in the content of cytosolic calcium. Local changes in the concentration of Ca 2+ ions in the cytoplasm play an extremely important role in the processes of assembly (and disassembly) of actin and intermediate filaments, and in the organization of cortical microtubules. Calcium-dependent functioning of the cytoskeleton takes place in processes such as cyclosis, flagellar movement, cell division, and polar cell growth.

Sulfur is one of the essential nutrients necessary for plant life. Its content in plant tissues is relatively small and amounts to 0.2 - 1.0% based on dry weight. Sulfur enters plants only in oxidized form - in the form of sulfate ion. Sulfur is found in plants in two forms - oxidized and reduced. The main part of the sulfate absorbed by the roots moves to the above-ground part of the plant through xylem vessels to young tissues, where it is intensively included in the metabolism. Once in the cytoplasm, sulfate is reduced to form sulfhydryl groups of organic compounds (R-SH). From leaves, sulfate and reduced forms of sulfur can move both acropetally and basipetally into the growing parts of the plant and into storage organs. In seeds, sulfur is found primarily in organic form. The proportion of sulfate is minimal in young leaves and increases sharply as they age due to protein degradation. Sulfur, like calcium, is not capable of reutilization and therefore accumulates in old plant tissues.

Sulfhydryl groups are part of amino acids, lipids, coenzyme A and some other compounds. The need for sulfur is especially high in plants rich in proteins, such as legumes and members of the cruciferous family, which synthesize sulfur-containing mustard oils in large quantities. It is part of the amino acids cysteine and methionine, which can be found both in free form and as part of proteins.

One of the main functions of sulfur is associated with the formation of the tertiary structure of proteins due to covalent bonds of disulfide bridges formed between cysteine residues. It is part of a number of vitamins (lipoic acid, biotin, thiamine). Another important function of sulfur is to maintain a certain value of the redox potential of the cell through reversible transformations:

Insufficient supply of plants with sulfur inhibits protein synthesis, reduces the intensity of photosynthesis and the rate of growth processes. External symptoms of sulfur deficiency are pale and yellowed leaves, which manifests itself first in the youngest shoots.

Magnesium ranks fourth in terms of content in plants after potassium, nitrogen and calcium. In higher plants, its average content per dry weight is 0.02 - 3.1%, in algae 3.0 - 3.5%. There is especially a lot of it in young cells, generative organs and storage tissues. The accumulation of magnesium in growing tissues is facilitated by its relatively high mobility in the plant, which makes it possible to recycle this cation from aging organs. However, the degree of reutilization of magnesium is much lower than that of nitrogen, phosphorus and potassium, since part of it forms oxalates and pectates that are insoluble and cannot move throughout the plant.

Most of the magnesium in seeds is found in phytin. About 10-15% Mg is part of chlorophyll. This function of magnesium is unique, and no other element can replace it in the chlorophyll molecule. The participation of magnesium in the metabolism of plant cells is associated with its ability to regulate the work of a number of enzymes. Magnesium is a cofactor for almost everyone. enzymes that catalyze the transfer of phosphate groups are necessary for the operation of many of the enzymes of glycolysis and the Krebs cycle, as well as alcoholic and lactic acid fermentation. Magnesium in a concentration of at least 0.5 mM is required for the formation of ribosomes and polysomes, activation of amino acids and protein synthesis. With an increase in the concentration of magnesium in plant cells, enzymes involved in the metabolism of phosphate are activated, which leads to an increase in the content of organic and inorganic forms of phosphorus compounds in the tissues.

Plants experience magnesium starvation mainly on sandy and podzolic soils. Its deficiency primarily affects phosphorus metabolism and, accordingly, the energy of the plant, even if phosphates are present in sufficient quantities in the nutrient substrate. Magnesium deficiency also inhibits the conversion of monosaccharides into polysaccharides and causes serious disturbances in the processes of protein synthesis. Magnesium starvation leads to disruption of the plastid structure - the grana stick together, the stromal lamellae are torn and do not form a single structure, instead many vesicles appear.

An external symptom of magnesium deficiency is interveinal chlorosis, associated with the appearance of spots and stripes of light green, and then yellow color between the green veins of the leaf. The edges of the leaf blades will turn yellow, orange, red or dark red. Signs of magnesium starvation first appear on old leaves, and then spread to young leaves and plant organs, with leaf areas adjacent to the vessels remaining green longer.

3. The role of silicon and iron

Silicon is found in all plants and accumulates in large quantities in the cell walls. Silicon is deposited in the cell wall and intercellular spaces in the form of hydrated amorphous silicates (SiO 2 ·nH 2 O). It is also capable of forming complexes with polyphenols and, like lignin, providing the mechanical strength of the cell wall - its rigidity and elasticity. Plants that accumulate Si have very strong stems (for example, cereal straw). Silicon helps increase plant resistance to fungal diseases. Diatoms build their shells by concentrating it from the environment. Silicon deficiency can stunt plant growth. Its deficiency has a particularly negative effect during the reproductive stage of development of the plant organism. When silicon is excluded from the nutrient medium, serious disturbances in the structure of cellular organelles are observed.

Iron is contained in plants in an average amount of 0.02 - 0.08% (20 - 80 mg per 1 kg of dry weight). In 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 initial stages chlorophyll synthesis (formation of d-aminolevulinic acid and protoporphyrins). 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.

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. It is orange-brown in color and consists of the colorless protein apoferritin and several thousand iron atoms in the form of basic compounds with hydroxyl and phosphate groups.

Bibliography

1. Malinovsky V.I. Plant physiology: Textbook. allowance. - Vladivostok: Far Eastern State University Publishing House, 2004.

2. Medvedev S.S. Plant physiology: Textbook. - St. Petersburg: St. Petersburg Publishing House. Univ., 2004. - 336 p.

3. Polevoy V.V. Plant Physiology: Textbook. for biol. specialist. universities - M.: Higher. school, 1989. - 464 p.

4. Plant physiology: Textbook for students. universities / N.D. Alekhina, Yu.V. Balnokin, V.F. Gavrilenko and others; Ed. I.P. Ermakova. - M.: Publishing center "Academy", 2005. - 604 p.

5. Plant physiology. Online encyclopedia [Electronic resource]. -http://fizrast.ru/kornevoe-pitanie/fiz-rol/makro-mikro/makroelementy.html - (date accessed 12/07/2012).

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In addition to proteins, fats and carbohydrates, a person needs numerous elements found in food for normal life. Plants also need additional nutrition with microelements.

Microelements are chemical elements necessary for the normal functioning of plants and used by plants in micro quantities compared to the main components of nutrition. However, their biological role is great.

All plants, without exception, need microelements to build enzyme systems - biocatalysts, among which the most important are iron, manganese, zinc, boron, molybdenum, cobalt, etc. A number of scientists call them “elements of life,” as if emphasizing that in the absence of these elements, the life of plants and animals becomes impossible. A lack of microelements in the soil does not lead to the death of plants, but causes a decrease in the speed and consistency of the processes responsible for the development of the organism. Ultimately, the plants do not realize their potential and produce a low and not always high-quality harvest.

Agricultural plants, based on their supply of microelements, are grouped into the following groups:

1. Plants with low removal of microelements and relatively high absorption capacity - grain bread, corn, legumes, potatoes;

2. Plants with increased removal of microelements with low and medium absorption capacity - root crops (sugar, fodder, table beets and carrots), vegetables, perennial herbs (legumes and cereals), sunflower;

3. Plants with high removal of microelements - agricultural crops grown under irrigation conditions against the background of high doses of mineral fertilizers.

Provincial features of the distribution of microelements are also associated with the lithological features of Quaternary deposits (Table 1).

Microelements cannot be replaced by other substances and their deficiency must be replenished, taking into account the form in which they will be in the soil. Plants can use microelements only in a water-soluble form (the mobile form of a microelement), and the immobile form can be used by the plant after complex biochemical processes involving soil humic acids have occurred. In most cases, these processes proceed very slowly and with abundant watering of the soil, a significant part of the resulting mobile forms of microelements is washed away.

All microelements of life, except boron, are part of certain enzymes. Boron is not part of enzymes, but is localized in the substrate and participates in the movement of sugars through membranes due to the formation of a carbohydrate-borate complex.

Most microelements are active catalysts that accelerate a number of biochemical reactions. Microelements, with their remarkable properties in minute quantities, can have a strong effect on the course of life processes and are very reminiscent of enzymes. The combined influence of microelements significantly enhances their catalytic properties.

In some cases, only compositions of microelements can restore normal plant development. However, reducing the role of microelements only to their catalytic action is incorrect.

Microelements have a great influence on biocolloids and influence the direction of biochemical processes. Thus, manganese regulates the ratio of divalent and trivalent iron in the cell. The iron-manganese ratio should be greater than two. Copper protects chlorophyll from destruction and helps to approximately double the dose of nitrogen and phosphorus. Boron and manganese increase photosynthesis after plants freeze.

An unfavorable ratio of nitrogen, phosphorus, and potassium can cause plant diseases that can be cured with microfertilizers.

Micro- and ultramicroelements include all elements of the 5th, 6th and 7th periods of the D.I. system. Mendeleev, most of the elements of the 4th period and some elements of the 2nd period.

A coherent doctrine of microelements was created by the works of many domestic and foreign scientists (V.I. Vernadsky, A.P. Vinogradov, K.K. Gedroits, D.N. Pryanishnikov, V.V. Kovalsky, V.A. Kovda, R Mitchell, A. Pailge, J. Hodson, N.G.

Microelements play an important biochemical and physiological role in the life of plants, animals and humans. Both a lack of microelements in the diet and an excess are unfavorable.

Table 26

(Vinogradov A.P., 1950)

	Lithosphere		Plants (ash)

The ratio of content in soils and lithosphere for many microelements is quite similar: the more an element is in the lithosphere, the more it is in the soil, but there is no strict proportionality. If, for example, the lithium content in soils and lithosphere is almost the same, then there is more sulfur in soils, and more nickel, copper, and zinc in the lithosphere. One of the reasons for this distribution is the accumulation of many elements by living organisms, after the death of which microelements enter, first of all, into the soil. This is clearly seen in the example of elements - biophiles, the content of which in plant ash is many times higher than in the lithosphere and soils (Mo, Zn, Cu, I, B).

The positive effect of microelements is due to the fact that they take part in redox processes, carbohydrate and nitrogen metabolism, and increase plant resistance to diseases and adverse environmental conditions. Under the influence of microelements, the chlorophyll content in the leaves increases and photosynthesis improves. Many microelements are included in the active centers of enzymes and vitamins. Microelements affect the permeability of cell membranes and the supply of nutrients to plants. For example, manganese promotes the selective absorption of ions from the external environment; when it is excluded, the content of a number of elements in plants increases. Manganese affects the movement of phosphorus from aging leaves to young ones. Cobalt, copper, boron improve the supply of nitrogen to plants. Zinc changes the permeability of membranes to potassium and magnesium. The supply of magnesium to plants improves with a sufficient supply of copper, zinc and boron.

It has been experimentally proven that microelements are necessary for many important biochemical processes; a lack of elements slows down these processes and even stops them. Mo, Fe, V, Co, W, B, Mn, Zn are needed for protein, carbohydrate and fat metabolism; Mg, Mn, Fe, Co, Cu, Ni, Cr are involved in protein synthesis; in hematopoiesis – Co, Cu, Mn, Ni, Zn; in breath – Mg, Fe, Cu, Zn, Mn, Co.

Research by scientists has shown that even with low contents, many microelements can significantly affect soil formation processes and actively participate in them. All soil biochemical processes of accumulation, transformation, and transfer of organic compounds in the ecosystem largely depend on the level of content and set of microelements. At the same time, trace elements stimulate the activity of microorganisms. As a result, the processes of formation of humic substances from plant residues are intensified.

The content and distribution of microelements across genetic horizons is actively influenced by many processes in the formation of the soil profile (Table 27). During the humus-accumulative process, they accumulate in the upper part of the soil profile. The intensive development of eluvial processes (podzolization, lessivage, solodization) is accompanied by soil depletion and the removal of elements from individual horizons, accumulation in illuvial and gley horizons.

During the process of soil formation, microelements are redistributed in the soil profile, as a result of which they accumulate or are washed out from the upper horizons; their content can increase as a result of the application of fertilizers, man-made pollution, near volcanoes, etc. Therefore, territories with insufficient or excessive content of microelements are identified. Such territories A.P. Vinogradov called biochemical provinces.

Table 27

Participation of microelements in the most important soil processes

(Kovda V.A., 1973)

	Soils or soil education	Accumulating microelements
Small biological cycle	Plant litter, fresh or partially decomposed	Mo, Zn, Cu, B, I, Br, Se, Ni, U, Ba, Mn, Sr, V
Humus synthesis	Humic substances	B, I, Mn, Co, Cu, Mo, Zn, Ni, Pb, Br, F
Formation of clays and synthesis of colloids	Highly dispersed part of the soil	Mn, Fe, Cu, Co, V, Cr, Ni, Mo Li Rb, Cs, Ba, Sr, Pb, Zn, Mn, V, I, B
Illumination	Illuvial horizons	Cu, Ni, Co, V, Cr, Zn, Mo, B
Gleying	Gley horizon
Hydrogen accumulation	Northern meadow soils Southern meadow soils Salt marshes Tropical laterites	Mn,Cu,Ni,V,Co, V B, I, F, Li, Rb, Cs, Zn, Ca, Co Ti, V, Cr, Co, Ni, Cu

V.V. Kovalsky (1970) developed the biogeochemical zoning of the territory of Russia on the basis of which he identified four main biogeochemical zones.

Taiga-forest non-chernozem zone. The reactions of living organisms in this zone are caused by a lack of calcium, phosphorus, cobalt (73% of all soils), copper (70%), iodine (80%), molybdenum (53%), boron (50%), zinc (49%), optimum manganese content (72%), relative excess, especially in river floodplains, strontium (15%).

Forest-steppe and steppe chernozem. This zone is characterized by optimal soil content of calcium and cobalt (96% for gray forest soils and 77% for chernozem soils), copper (72-75%), manganese (71-75%), iodine, zinc, molybdenum are balanced with other elements. Sometimes there is a lack of mobile manganese.

Dry steppe, semi-desert, desert. Living organisms are affected by elevated levels of sulfate, boron (88%), zinc (76%), often strontium (47%), molybdenum (40%), low copper (40%), and sometimes cobalt (52%).

Mountain zones. Often there is a deficiency of iodine, cobalt, copper, zinc, although excess copper, zinc, cobalt, molybdenum, strontium, etc. are also possible.

Biogeochemical provinces are identified in each zone. Thus, in provinces with a lack of cobalt, the synthesis of vitamin B12 is weakened, which is typical for the Non-Black Earth Zone; with a lack of iodine, the function of the thyroid gland is impaired and endemic goiter occurs; With an excess of selenium, hoof deformation and hair loss in animals occur. The territory of Belarus, especially Polesie, is characterized by a lack of iodine in waters and soils, as a result of which goiter is observed, with a lack of cobalt, leukemia develops (tachycardia in the Baltic states), an excess of molybdenum in Northern Kazakhstan, Tuva, Armenia causes gout, etc.

Insufficient or excessive content of microelements in soils is due to two groups of reasons:

Biochemical characteristics of soils and landscapes;

The influence of technogenic flows of substances.

Provinces with a high content of elements are formed in areas with a predominance of accumulative landscapes, as well as near ore deposits, in zones of volcanic activity, as a result of technical pollution of the territory.

The primary sources of microelements are rocks, partly atmospheric air and soil and groundwater. Microelements are consumed by plants from the soil, but some elements enter plants from air and water. Microelements can enter the soil with atmospheric gases, volcanic smoke, meteorite precipitation when applying pesticides to combat plant diseases and pests, and with mineral fertilizers.

Microelements in soils are contained: in the crystal lattice of primary and secondary minerals in the form of an isomorphic mixture; in the form of insoluble compounds (salts, oxides); in an ion exchange state; as part of organic matter; in soil solution.

One of the criteria for the degree to which plants are supplied with microelements is their content in the soil. In this case, what is most important is not the gross (total) amount of individual microelements in the soil, but the presence of mobile forms, which determine their availability to plants (Table 28).

Table 28

(Rinkis G.Ya., 1982), mg/kg

The availability of microelements for plants is determined by their content in the soil solution and in the ion exchange state. The predominant part of microelements contained in the soil is inaccessible to plants. Thus, mobile compounds of Cu, Co, Mn make up only 10-25% of their total amount, the proportion of available zinc and molybdenum compounds is less, sometimes up to 1%.

The number of mobile forms in soils varies greatly, which is explained by the genetic characteristics of the soils and the intensity of their cultivation.

Table 29

Average amount of microelements * and content of mobile forms ** in arable soil horizons of the Middle Urals,

mg/kg in extracts according to Peive-Rinkis according to Kuznetsov M.F.


(Kovrigo V.P., 2000)
Soddy-podzolic sandy loam and sandy
Sod-podzolic loamy
Gray forest podzolized loamy and clayey
Sod-carbonate clayey
Sod-gley clayey

Alluvial loamy

Note: *numerator, **denominator

The content of microelements in mobile form is determined by the type of soil, the nature of the parent rocks and vegetation, the microbiological activity of the soil, the reaction of the environment, and the content of organic matter. For example, acidification increases the mobility of Mn, Cu, B, Zn, etc., but the availability of Mo decreases significantly. Humic acids, as well as formic, citric and others, can form both soluble and insoluble compounds with microelements.

The main patterns in the content and distribution of microelements in soddy-podzolic soils of the Perm region were studied by T.A. Krotkikh, G.Ya. Elkina.

It has been established that the provision of soddy-podzolic soils with forms of microelements accessible to plants is determined by gross reserves (mainly in soil-forming rocks), the degree of podzolization, and granulometric composition.

The gross amount of microelements in the arable horizon closely correlates with their reserves in soil-forming rocks.

Their number increases from soils of light to heavy texture, from highly podzolized to less podzolized soils (Table 30).

Table 30

soddy-podzolic soils of the Perm region, mg/kg

(Elkina G.Ya., 1980)

Bor widely distributed in nature in the form of oxygen compounds of boron-containing minerals boric acid (H 3 BO 3) and borax. Its content in the lithosphere reaches 3010 -3% (Na 2 B 4 O 7 10H 2 O). Fluctuations in boron content in soils range from 2 to 130 mg/kg. The average boron content in plant ash is 0.04%. Dicotyledonous plants need boron the most. Significant content of this element is found in flowers, especially in stigmas and styles.

Boron has a great influence on the metabolism and transport of carbohydrates in plants; With a lack of boron, the outflow of carbohydrates from leaves into roots and tubers is delayed. Boron deficiency reduces the number of fertilized flowers, disrupts the process of seed ripening, and reduces the fixation of atmospheric nitrogen by nodule plants.

The most boron-poor soils are soddy-podzolic soils, especially sandy and sandy loam, soddy-gley, swampy soils of light granulometric composition. In chernozems, the amount of boron ranges from 0.3 to 1.8 mg/kg; most of all in brown steppe soils, where salt accumulations and boron solonchaks occur. An excess of boron is observed in some biogeochemical provinces, one of them is located in the river basin. Ural.

With a lack of boron, plants are affected by dry rot (roots), brown rot ( cauliflower), bacteriosis. Sunflower, alfalfa, fodder root crops, flax, rice, etc. are especially sensitive to boron deficiency. vegetable crops, sugar beet.

Excess boron causes leaf burn. A good supply of plants with calcium and phosphorus increases the requirements for boron supply. Liming reduces the availability of boron and fixes it in the soil. The application of boron on calcareous soils completely eliminates the disease of root crops with core rot and potato scab. The introduction of boron is advisable if the content of mobile forms in the soils of the Non-Chernozem Zone is less than 0.2-0.5 mg per 1 kg of soil.

Copper. The average copper content in plants is 0.0002% or 2 mg per 1 kg of weight and depends on their species characteristics and soil conditions. The average copper content in the lithosphere is 10∙10 -3, and in soils 2∙10 -3%. With the harvest different cultures 7-327 g of copper is removed from 1 ha. Copper increases plant resistance to lodging; helps to increase the drought, frost and heat resistance of plants. Lack of copper causes growth retardation, loss of turgor and wilting of plants, and delayed flowering. In fruit trees, when there is a lack of copper, dryness appears.

The gross content of copper in various soils ranges from 0.1 to 150 mg per 1 kg of soil. High peat bogs, soddy-carbonate soils, sandy and sandy loam soils are the poorest in copper. Liming of acidic soils reduces the supply of copper to plants. Lime acts as a copper adsorbent. Soils are considered poor in copper content if the soils of the Non-Chernozem Zone contain copper< 1,5–2,0 мг, в черноземной зоне - < 2,0–5,0 мг на 1 кг почвы. Потребность в меди возрастает в условиях применения высоких доз азотных удобрений. Наиболее отзывчивы на медные удобрения пшеница, овес, ячмень, травы, лен, корнеплоды, просо, подсолнечник, горох, овощные культуры и плодово-ягодные.

Manganese . Cereals, beets, fodder root crops, potatoes, raspberries, and apple trees are especially demanding of sufficient levels of available forms of manganese in the soil. With the crop harvest, 1000-4500 g of manganese are removed from 1 hectare.

Manganese is necessary for all plants. The average Mn content in plants is 0.001% or 10 mg per 1 kg of weight. Its main quantity is localized in leaves and chloroplasts. The direct participation of Mn in photosynthesis has been revealed. Manganese plays a large role in activating many reactions in plants. Manganese increases the water-holding capacity of tissues, reduces transpiration, and affects plant fruiting. In cases of acute manganese deficiency, cases of complete absence of fruiting have been reported in radishes, cabbage, tomatoes, and peas.

Manganese in soddy-podzolic and chernozem soils contains 0.1-0.2%, but most of this element is in the form of sparingly soluble oxides and hydroxides. If the total content of Mn in the arable horizons of the main soils ranges from 0.05 to 0.29%, then the amount of mobile (according to Peive) Mn in soddy-podzolic soils is 50-150 mg/kg, and in soils of other types - from 1.0-1.5 to 75-125 mg/kg.

First of all, manganese fertilizers should be applied on gray forest soils, slightly leached chernozems, saline and chestnut soils.

Molybdenum . The highest content of molybdenum in plants was observed in legumes (0.5-20.0 mg per 1 kg of dry weight), and in cereals from 0.2-1.0 mg per 1 kg of dry weight.

Molybdenum is needed by plants in smaller quantities than boron, manganese, zinc and copper. Molybdenum is localized in young growing organs.

If there is a lack of molybdenum in the nutrient medium, nitrogen metabolism in plants is disrupted, and large amounts of nitrates accumulate in the tissues. Molybdenum is involved in the biosynthesis of nucleic acids, photosynthesis, respiration, and the synthesis of pigments and vitamins.

Acidic soils are the poorest in available forms of molybdenum. The content of gross molybdenum in soil ranges from 0.2 to 2.40 mg, and mobile forms - from 0.10 to 0.27 mg per 1 kg of soil. The poorest molybdenum soils are light-textured soils with low humus content. The lowest content of mobile molybdenum was observed in soddy-podzolic sandy soils (0.05 mg per 1 kg). Higher content of total and mobile forms of molybdenum in chernozem soils.

Zinc. The removal of zinc from field crops ranges from 75 to 2250 g per 1 ha. Buckwheat, hops, beets, potatoes, and meadow clover are characterized by increased sensitivity to zinc deficiency. Weeds are characterized by a higher zinc content than cultivated plants. Coniferous plants have an increased content of zinc; the highest zinc content is found in poisonous mushrooms. The need for zinc in field crops is lower than in fruit trees.

Zinc increases the heat and frost resistance of plants and is involved in the formation of chlorophyll precursors. More than 30 zinc-containing enzymes are known. With a lack of zinc in plants, the content of sucrose and starch decreases, the auxin content decreases, protein synthesis is disrupted, cell division is suppressed, which leads to morphological changes in leaves, cell elongation and tissue differentiation are impaired.

Zinc deficiency can manifest itself both on acidic, highly podzolized light soils, and on carbonate soils poor in zinc, and on highly humus-rich soils. The occurrence of zinc deficiency is enhanced by the use of high rates of phosphorus fertilizers and strong plowing of the subsoil to the arable horizon. The highest gross zinc content is in tundra (53-76 mg per 1 kg) and chernozem (24-90 mg per 1 kg) soils, the lowest in soddy-podzolic soils (20-67 mg per 1 kg). Zinc deficiency most often occurs on neutral and slightly alkaline carbonate soils. In acidic soils, zinc is more mobile and available to plants.

Cobalt. The average cobalt content in plants is 0.00002%. Cobalt is necessary for the biological fixation of molecular nitrogen and is a component of vitamin B12. Cobalt deficiency can manifest itself primarily in legumes. With a low cobalt content in feed, animals develop anemia, their appetite sharply decreases, and their productivity drops. The positive effect of cobalt is primarily manifested on soils that are well supplied with all other elements of mineral nutrition, with a reaction close to neutral.

An agrochemical survey showed that the soils of individual biochemical provinces are often poor in mobile forms of some microelements. B.A. Yagodin and I.V. Vernichenko made a generalization of the literature on the provision of soils in the main biogeochemical zones of Russia with mobile forms of microelements, established on the basis of analysis of soils and plants, as well as as a result of field and vegetation experiments (Table 31).

For agronomic purposes, the gross and mobile amounts of microelements (mg/kg) are determined in soils. Indicators of the content of mobile elements in soils are used to determine the need to use microfertilizers. There is a grouping according to the supply of plants with mobile forms of microelements (Appendix 4).

Table 31

Gradations of the supply of Russian soils with mobile forms of microelements

(Agrochemical characteristics of soils of the USSR, 1962-1974)

Micro element	Biochemical zone	Soil	Availability gradations, mg per 1 kg of soil
Micro element	Biochemical zone	Soil	very poor	very rich
	Taiga-forest

		Oxalate extract
		0.1 n. H2SO4


	Forest-steppe and steppe

		Oxalate
		0.1 n. H2SO4


	Dry-steppe and semi-steppe
		HNO 3 (according to Gyulakhmedov)

hood 1n. HCl

hood 1n. KCl

extract 0.1 N H2SO 4

hood 1n. НNO 3

Mo in oxalic acid extract
(according to Grieg)

In aqueous extract

Podzolic:
minimum
maximum

Carbonate
Non-chernozem zone:
minimum
maximum

Chernozems:
minimum
maximum

Chestnut:
minimum
maximum

Serozems:
minimum
maximum