The role and physiological effect of phytohormones in the development of crop plants

How phytohormones work and where they are produced

A plant coordinates the development of its cells, tissues, and organs with the help of phytohormones — low-molecular-weight organic compounds. These substances convert external environmental signals into biochemical information to launch growth programs. Phytohormones are produced from photosynthesis and respiration products — amino acids and organic acids.

The action of phytohormones extends to the entire organism, creating a unified hormonal field. Depending on the developmental stage, they temporarily change enzyme activity or cause lasting changes in physiological processes. The most active regulators include auxins, gibberellins, cytokinins, abscisic acid, and ethylene.

• Plant hormone requirement — 10⁻¹⁰–10⁻⁵ mol/L
• Main groups of regulators — 5 classes
• Auxin synthesis — stem tips and seed
• Cytokinin synthesis — plant roots

Plants lack specialized internal secretion organs like those of livestock animals. Hormones are synthesized in meristematic tissues or leaves, after which they are distributed throughout the organism. The direction of this movement is strictly defined for each group of substances:

• Auxins (IAA) move from stem tips and seed downward (basipetally) to lateral shoots and leaves.
• Gibberellins (GA) and abscisic acid (ABA) are synthesized in leaves and transported both up and down the stem. ABA is also produced in the root cap.
• Cytokinins (CK) originate from roots and move exclusively up the stem (acropetally).

The role of auxins and gibberellins in crop management

Auxins are compounds of a predominantly indole nature. They initiate cell division, regulate the formation of conducting bundles, and are responsible for stem bending toward light or ground (photo- and geotropism). Cell elongation occurs because auxin stimulates the secretion of H⁺ ions into the cell wall, activating the enzymatic cleavage of cellulose bonds.

In field and greenhouse conditions, auxins are used to stimulate root formation in cuttings and prevent the shedding of leaves or fruit set. These substances also induce parthenocarpy — the formation of seedless fruits. Due to the attracting effect, tissues treated with auxin are able to draw nutrients from other parts of the plant.

Gibberellins are derivatives of the fluorene series. They actively stimulate cell division and elongation in apical and intercalary meristems. Under their influence, leaves, stems, flowers, and inflorescences elongate, with them affecting stem growth significantly more strongly than auxins.

In agronomic practice, gibberellins are used to accelerate seed germination and stimulate the transition of long-day crops to flowering. They contribute to the setting of parthenocarpic fruits and influence nucleic metabolism. Under the influence of the hormone, messenger RNA is synthesized, triggering the production of hydrolytic enzymes, primarily α-amylase.

Cytokinins are phytohormones, predominantly purine derivatives. They stimulate cytogenesis, seed germination, and also promote bud differentiation. In addition, cytokinins have the ability to delay the aging processes of plant organisms and maintain normal metabolism in yellowing leaves, as well as cause their secondary greening. They play a major role in mobilization – the drawing of nutrients to the places of their localization: fruits, seed, tubers. Cytokinins release lateral buds from apical dominance caused by auxin and stimulate their growth. At the molecular level, cytokinins in complex with a specific protein receptor enhance the activity of RNA polymerase and the template activity of chromatin; this increases the number of polyribosomes and protein synthesis. Cytokinins are involved in the synthesis of the enzyme nitrate reductase, as well as in the transport of H+, K+, and Ca2+ ions.

Abscisins are natural inhibitors of a terpenoid nature. These phytohormones delay growth in the cell division and elongation phase without showing toxic effects even at high concentrations. They induce a dormant state in plants, accelerate the shedding of leaves and fruits (abscission), inhibit coleoptile growth, and delay seed germination. Abscisins, by restraining excessive stem growth, direct metabolites toward the formation of the photosynthetic apparatus; in other words, they coordinate the growth process. One of the most important functions of abscisins is their participation in stress mechanisms by regulating stomatal movements. Abscisic acid accumulates rapidly in tissues under the influence of unfavorable environmental factors, especially during water deficit, causing rapid stomatal closure, which reduces transpiration and cuts energy costs. At the molecular level, abscisins can inhibit DNA, RNA, and protein synthesis. They can also reduce the functional activity of the H+ pump, which can have diverse consequences.

Ethylene is a specific hormone synthesized in all plant organs from methionine. It contributes to the regulation of plant growth and development. In particular, it is involved in maintaining the apical hook in dark-grown seedlings and causes epinasty* in leaves and petals. Therefore, it is used to accelerate flower opening. The downward drooping of leaves under the influence of ethylene reduces transpiration. Ethylene is directly responsible for auxin-controlled inhibition of lateral bud growth in plants exhibiting apical dominance. It inhibits cell division and seedling elongation, changing the direction of cell growth from longitudinal to transverse, which leads to a decrease in length and thickening of the stem. By promoting tissue aging, ethylene accelerates leaf abscission, flower wilting, and rapid fruit ripening. In most cases, this hormone increases the dormancy period of seed and tubers, promotes a shift in plant sex towards the female side, and also acts as a mediator of the hormonal complex in the processes of correlative interactions within the plant. Ethylene inhibits polar auxin transport and promotes the formation of its conjugates. Furthermore, ethylene regulates the stress response in plants. At the molecular level, ethylene increases the permeability of cell membranes and the rate of protein synthesis.

Brassinosteroids are hormones that maintain the plant immune system in a normal state, especially in stress situations: temperature drops, frosts, flooding, drought, diseases, pesticide action, and soil salinity. Steroids belong to the terpenoid class, which also includes gibberellins and abscisic acid.

Epinasty is the rapid growth of the upper side of an organ, resulting in the leaf or petal bending downwards.

Brassinosteroids are contained in every plant cell, but their natural level in a changing ecological situation is often not high enough to maintain immunity and normal development throughout the entire growing season of plants.

Thus, the effect of the above-mentioned hormones on metabolism of the plant organism is specific: gibberellins participate in transcription**, cytokinins – in translation***, auxins – in changing membrane permeability, abscisins inhibit ion transport and related cell growth processes, and ethylene acts as a "permissive" growth factor, controlling the balance in the stimulator-inhibitor system.

Plant growth regulators allow for enhancing or weakening plant traits and properties within the limits of the genotype's norm of reaction. Consequently, they are an integral part of comprehensive chemicalization in crop production. With the help of growth regulators, the shortcomings of cultivars and hybrids of crop plants are compensated; therefore, they do not have universal significance and cannot replace other factors of yield formation. In this regard, it is extremely important to know precisely the mechanism of their action at the physiological-biochemical, molecular, and genetic levels. Determining this has allowed for the synthesis of appropriate preparations that have found application in crop production. Modern agriculture cannot do without the use of environmentally safe, genetically harmless plant growth regulators.

Phytohormones – auxins, gibberellins, cytokinins, ethylene, and abscisins have not directly gained economically significant practical distribution. However, the idea of using them as endogenous growth regulators and plant development regulators has ultimately led to the creation of synthetic preparations with similar effects. To date, over 5,000 compounds with regulatory action have been discovered, but only about 50 are used in global practice. This indicates that their widespread industrial application is only just beginning.

Four rules of efficiency and working with auxins

Growth regulators are successfully used in horticulture, for protecting cereals against lodging, controlling weeds, and also for preventing the sprouting of tubers and bulbs during storage. However, high efficiency of treatments is achieved only when strict conditions are met. Preparations yield a noticeable result if the plant itself or its individual organs lack endogenous phytohormones, and the cells are receptive to the treatment. At the same time, treated crops and plantings must be fully provided with moisture and nutrients.

In agricultural practice, preparations of an auxin nature are the most in-demand. This list includes 1-naphthaleneacetic acid (1-NAA), indole-3-butyric acid (IBA), 2,4-dichlorophenoxyacetic acid (2,4-D), 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), 2-naphthoxyacetic acid (2-NOA), 4-chlorophenoxyacetic acid (4-CPA), 2,4-dichlorophenoxybutyric acid (2,4-DB), as well as maleic hydrazide (MH) and 2-methyl-4-chlorophenoxyacetic acid (MCPA). They are used to stimulate root formation, produce seedless fruits, thin out flowers and fruit set, suppress stem elongation, and accelerate ripening.

For rapid rooting of cuttings and improved survival rates of fruit crop transplants, 1-NAA and IBA are used. These preparations help to quickly restore the root system of transplanted trees and shrubs in a new location. Treatment is carried out by soaking planting material before planting.

1. Prepare an aqueous solution of the preparation with an active ingredient concentration of 50–70 ml/l.
2. Immerse the cuttings in the prepared solution for 12–24 hours.

To produce seedless fruits and stimulate fruit set in tomatoes, cucumbers, eggplants, and peppers, plantings are sprayed with a solution of 2-NOA or 4-C during the flowering period. To prevent pre-harvest fruit drop in orchards, 1-NAA and 2,4-D are used by treating the canopy of trees during fruit formation. MH and 1-NAA methyl ester help to delay the sprouting of potatoes, onions, and root crops during long-term storage. Potatoes are treated before storage with a mixture of 2–3% 1-NAA methyl ester and clay, while MH is applied to the vegetative tops 2–3 weeks before harvesting. This method helps preserve sucrose in beet root crops and also inhibits the sprouting of carrots and onions during long-term storage.

• 1-NAA and IBA concentration for cuttings — 50–70 ml/l
• 2-NOA and 4-C solution for spraying vegetables — 40–50 ml/l
• 1-NAA and 2,4-D solution against fruit drop — 0.0001–0.001%
• Dose of 1-NAA ester for potato treatment — 50–100 g/t
• MH solution for spraying tops — 0.2%
• Anti-sprouting protection period at 10–15 °C — 8 months

Practice of using gibberellins on crops

Gibberellins are widely used to increase yield and regulate ripening times for various crops. Spraying vineyards during flowering increases the yield of seedless sultana cultivars by 10–15%. On orange trees, treatment applied to green fruits delays ripening and improves the mechanical properties of the peel, extending storage life. In hemp cultivation, spraying crops twice with gibberellin increases fiber yield by 8–12%.

When performing a second summer potato planting, gibberellin is used to quickly break the dormancy of freshly harvested tubers. The preparation stimulates the buds into active sprouting. For this, the planting material undergoes mandatory pre-treatment with an aqueous solution.

1. Prepare an aqueous solution of gibberellic acid at a rate of 1–2 mg/l.
2. Cut the tubers and immerse them in the solution for 30–60 minutes.

In rice crops, pre-sowing seed treatment with a gibberellic acid solution significantly improves the quality of emergence. This practice increases the field germination of seed and ensures the formation of an optimal productive stand density. The results of field trials of various growth regulators on rice are presented in the table.

• Gibberellic acid consumption on grapes — 30–35 g/ha
• Yield increase for sultana cultivars — 10–15%
• Gibberellin consumption on hemp — 20 g/ha
• Increase in hemp fiber yield — 8–12%
• Soaking time for potato tubers — 30–60 min
• Solution concentration for potatoes — 1–2 mg/l

Efficiency of pre-sowing seed treatment of rice with growth regulators

Preparation	Laboratory germination, %	Field germination, %	Germination energy, %	Germination speed, days	Uniformity of germination, units/day	Grain yield, cwt/ha
Control (untreated)	92.6	27.2	71.4	3.0	11.6	64.9
Oxyhumate	94.0	33.8	81.6	2.9	14.8	71.0
Gibberellic acid (GA)	98.5	38.3	86.0	2.8	15.2	74.8
Succinic acid (SA)	91.6	29.6	75.5	2.9	14.1	66.5
Mival	95.0	32.7	76.0	2.9	13.0	68.5
Kartolin	93.5	30.6	74.0	2.9	12.5	68.3
Crotonolactone	92.5	32.4	80.6	2.9	13.6	70.1
Brassinolide	92.6	36.8	78.6	2.9	14.5	73.2
Quartazin	92.8	31.4	78.4	2.9	14.8	69.9

Cytokinins and ethylene: managing branching and ripening

Cytokinins are used both in laboratories for tissue culture propagation and directly in the field or orchard. They help regulate plant form: they reduce apical dominance and stimulate branching, allowing for bushier forms. Furthermore, these hormones help delay leaf senescence, increase resistance to environmental stress factors, stimulate flowering, and can shift sex expression towards the female side.

Ethylene effectively accelerates the ripening of harvested fruits and vegetables. To do this, fully formed but still green fruits are placed in airtight chambers with controlled temperature and gas is applied periodically. This technology shortens ripening times several-fold.

• Temperature in the chamber — 20–22 °C
• Ethylene dosage — 0.2–1.0 l/m³
• Tomato ripening — 5–6 days (instead of 10–12)
• Citrus ripening — 4–5 days (instead of 20–25)

Plant growth retardants: protecting cereals from lodging

Retardants are synthetic growth inhibitors that suppress gibberellin synthesis. They act selectively: they slow down the cell division of the stem in length, but increase their division in the transverse direction. As a result, the stem shortens and thickens, while the apical meristem, responsible for leaf and ear formation, continues to develop without delay. The plant's mechanical tissue strengthens, roots expand, and leaf area increases.

The effect of a retardant on the anatomical structure of the stem, using the Krasnodarsky 86 rice cultivar as an example:

Variant	Thickness of mechanical tissue ring, µm	Thickness of filled part of the stem, µm	Diameter of vascular bundles, µm	Number of vascular bundles, pcs.
Control (untreated)	39.2	1101.8	176.3	46.2
Sumadik	42.8	1152.4	188.7	50.8

Based on their chemical structure and mechanism of action, retardants are divided into four main groups:

• Quaternary onium compounds (chlormequat chloride or CCC, morphol, pix) — block gibberellin biosynthesis at early stages, interfering with the formation of geranylgeranyl pyrophosphate and its cyclization into ent-kaurene.
• Triazole derivatives (paclobutrazol, uniconazole) — stop gibberellin synthesis by blocking the oxidation of ent-kaurene into kaurenoic acid.
• Ethylene-releasing preparations (2-chloroethylphosphonic acid or 2-CEPA and its salts) — act as antigibberellins at the stage of hormone binding to the receptor or during the subsequent realization of its activity.
• Hydrazine derivatives (2,2-dimethylhydrazide succinic acid, maleic acid hydrazide sodium salt) — suppress the hormonal activity of already synthesized gibberellins.

Chlormequat chloride (CCC), also known as Tur, is of the greatest practical importance. It is successfully used on wheat, rye, barley, oat, and rice crops.

Efficiency of applying various retardant preparations on Krasnodarsky 86 rice crops:

Retardant and dosage	Plant height, cm	Panicle length, cm	Lodging, points	Grain yield, c/ha
Control (untreated)	118.5	17.1	2	52.6
CCC, 10 kg/ha	112.3	17.3	4	56.9
Oriz, 30 kg/ha	100.5	16.9	5	59.0
Sumadik, 30 kg/ha	98.3	17.0	5	60.8

New generation anti-stress agents, retardants, and biostimulants

In modern crop production, the focus is shifting toward environmentally safe and physiological growth regulators. In rice farming, the retardants "Oriz" and "Sumadik" show high efficiency — they inhibit stem elongation and work directly to increase yield. In vegetable farming, a 0.5% aqueous solution of chlormequat chloride solves the problem of seedling etiolation in dense plantings. After such treatment, plants take root better during transplanting, which ultimately increases the harvest. Floriculture farms use similar preparations on carnation, peony, and chrysanthemum plantings to prevent excessive peduncle elongation under sunlight deficiency.

"Brassinolid" is used to improve the overall resistance of plants to adverse factors. It is a low-toxicity and safe preparation recommended for seed treatment and spraying of crops during the growing season.

• Active ingredient — 100% brassinolid
• Chemical formula — C28H48O6
• Solubility — in ethanol (insoluble in water)

The "Viva" biostimulant works simultaneously as a growth stimulant and a soil restorer. The preparation provides a complex synergistic effect on the aerial part of plants and their root system. It is recommended for the regeneration of beneficial microflora after treatments with harsh pesticides — for example, soil herbicides or nematicides. "Viva" contains proteins, peptides, amino acids, polysaccharides, humic acids, vitamins, as well as calcium and magnesium. In sandy soils, the preparation can be applied with every irrigation via drip systems at an application rate of 0.4 l/ha.

Crop	Treatment timing and phases	Application rate
Tomatoes, zucchini, melon, eggplants, pepper, cucumbers	15–20 days after transplanting; at the fruit set stage on the first cluster; then every 20–25 days	1–2 l/1000 m²
Strawberry	15–20 days after transplanting; at the beginning of vegetative growth; after fruit formation	0.5–1 l/1000 m²
Legumes	At the 2–3 leaf stage; then every 15–25 days	0.3–0.5 l/1000 m²
Carnations, chrysanthemums	15–20 days after transplanting; before flowering; after the first harvest	2 l/1000 m²
Bulbous and root crops	At the beginning of stem growth; before flowering	2 l/1000 m²
Roses	After pruning; at the budding stage; 20–25 days after the second treatment	2–3 l/1000 m²
Citrus, grape, pear, kiwi	At the flowering stage; after fruit formation	10–15 l/ha
Stone fruits	After fruit set formation	5–6 l/ha

The environmentally friendly stimulant "Harmonia" is produced from peat and contains active components of the humus complex. The preparation is supplied as a dark, thick liquid. Its action is aimed at stimulating seed germination, accelerating root formation, as well as activating photosynthesis and carbohydrate metabolism during the growing season.

Methods of applying the "Harmonia" preparation:

• seed treatment;
• spraying of growing plants;
• combined scheme (seed treatment followed by spraying during the growing season).

The application of the stimulant can be combined in tank mixtures with pesticides and foliar top dressing with macro- and microelements.

"Harmony" stimulant application parameter	Regulation
Product application rate	0.4–4.0 l/ha
Dilution with water (working concentration)	1:100 (1 %) or 1:1000 (0.1 %)

Classic phytohormones: gibberellin and heteroauxin

Gibberellin is produced via microbial synthesis. The product is a white powder containing up to 80–85 % of active ingredient — gibberellic acid (a natural phytohormone). The substance is highly soluble in alcohol and alkalis but poorly soluble in water. Gibberellin has a pronounced effect on plants: it accelerates shoot and fruit growth, manages flowering, and stimulates the germination of stems and tubers. Due to its high physiological activity, weak concentrations are used for treatments — from 1 to 200 mg of the product per 1 l of water. The working solution is used for pre-sowing seed treatment and spraying of crops during the growing season.

When preparing a working solution of gibberellin, it is important to follow the correct sequence of actions.

1. Dissolve 1 g of the dry product in 20 ml of alcohol (alternatively, 0.5% aqueous ammonia or a 0.5% solution of soda ash can be used instead of alcohol).
2. Dilute the resulting solution with water to the required working volume.

Heteroauxin is also included in the group of natural growth regulators. This product is indispensable for activating root formation. It is used for treating the root system of transplants before planting, soaking bulbs, and stimulating root development in plants throughout the growing season.

Treatment of planting material of tulips, gladioli, crocuses, and some other crops halves the rooting period, which is especially important for the vegetative propagation of flowers. Abundance of roots contributes to faster development of shoots and leaves. The product is produced in the form of solutions, powders, or paste. Working solutions are prepared immediately before use. Optimal concentrations: 50–200 mg of active ingredient per 1 l of water.

Maleic hydrazide (MH) is a white crystalline substance, poorly soluble in water. In agricultural practice, products prepared on the basis of its water-soluble salts are used:

• Diethanolamine (MH-D)
• 3-ethanolamine (MH-T)
• Sodium (MHNa)
• Ammonium (MH-NH4)

MH-D (MG-D) is a concentrated solution of MH in diethanolamine, containing 30–33 % of active ingredient.

MH-T (MG-T) is a solution of MH in 3-ethanolamine containing 30 % of active ingredient; a viscous, dark brown, almost odorless liquid.

MH-Na (MG-Na) is an aqueous solution of white crystalline sodium salt of MH, containing 40–80 % of active ingredient.

MH-NH4 (MG-A) is a light brown, transparent liquid containing 20–25 % MH, pH 7–8. Its composition includes a certain amount of ammonium sulfate, which does not reduce the activity of the product and simultaneously serves as a fertilizer.

MH is a systemic regulator; depending on the dose, it acts as a growth inhibitor or stimulant, or as a non-selective herbicide. It is used for:

• improving seed germination;
• increasing the shelf life of tubers, root crops, and bulbs during storage;
• preventing excessive shoot growth of vegetating plants;
• increasing seed yield and sugar content of sugar beet.

Average application rates are 1.25–2.5 kg/ha of active ingredient.

Gibbersib (50% aqueous solution) is used on open and protected ground tomatoes. Method of application: two- or three-time spraying of plants at the beginning of flowering of the first to third trusses with a 0.005–0.0075% solution to accelerate fruit ripening and increase yield.

Gidrel (40% aqueous solution) is used in the cultivation of food-grade potatoes. Method of application: spraying tubers when placing them into storage with a 0.5% solution to prevent tuber sprouting. Tubers can be sold 5 months after treatment.

The product is also applied to open-ground cucumber crops by spraying plants once at the two-to-three true leaf phase with a 0.025–0.03% solution to accelerate the onset of fruiting and increase yield.

On open-ground tomatoes, spraying plants when 10–30% of fruits are ripening with a 0.1–0.25% solution promotes uniform fruit ripening and an increase in early yield.

Immunocytophyte is a multi-purpose stimulant of plant defense responses, growth, and development.

Immunocytophyte is intended to increase resistance to diseases and adverse weather conditions, accelerate plant growth and development, fruit ripening, improve the taste and nutritional qualities of vegetables and fruits, reduce harvest losses during storage, and increase yield by 20–30 %.

Immunocytophyte increases disease resistance. It has no negative effects on plants. The product cannot cause poisoning and does not require hygienic regulation of working conditions during application, transport, or storage. Accumulation of the product in the environment and the possibility of contamination of groundwater and surface water are excluded. The product is safe for bees. Neutralization of the aqueous solution of the product is not required; waste and packaging of Immunocytophyte are disposed of in household waste collection points.

To treat 5 g of sunflower, pea, corn, and vegetable crop seeds (tomatoes, cucumbers, watermelons, cabbage, onions, beet, and carrots), the following steps must be performed:

1. Dissolve one tablet in 10–15 ml (a tablespoon) of cold water.
2. After 20–30 minutes, stir until completely dissolved.
3. Soak the seed and keep it in the resulting solution for 3–24 hours, depending on the crop, seed size, and planting technology.
4. Perform seed treatment immediately before sowing.

To treat 20 kg of potato tubers or bulbs, dissolve one tablet in 10–15 ml (a tablespoon) of cold water, stir after 20–30 minutes until completely dissolved, and add 140–150 ml of water to the solution. Spray the potato tubers or bulbs with the resulting solution 2–3 days before planting.

Immunocytophyte is used to spray growing vegetable crops, strawberries, potatoes, sunflowers, corn, peas, and ornamental bulbous flower crops. To treat 50 m2 of a crop of these plants, dissolve one tablet in 10–15 ml of cold water, stir after 20–30 minutes until completely dissolved, add 2 l of water to the solution, and spray the plants with the resulting solution.

Tomatoes: 1st spraying – bud formation initiation phase, 2nd – flowering of the first inflorescence, 3rd – flowering of the third inflorescence.

Cucumbers and watermelons: 1st spraying – 2–4 leaf phase, 2nd – beginning of flowering phase, 3rd – mass fruit set phase.

Cabbage: 1st spraying – rosette phase, 2nd – head formation phase (30–40 days after the first).

Onions: 1st spraying – 4–5 leaf phase, 2nd – 30–40 days after the first.

Strawberries: 1st spraying – beginning of peduncle differentiation, 2nd – mass flowering to end of flowering (14–16 days after the first).

Potatoes: 1st spraying – full emergence phase, 2nd – bud formation to beginning of flowering phase.

Sunflowers: 1st spraying – full emergence phase, 2nd – beginning of bud formation phase.

Corn: spraying at the 2–5 leaf phase.

Peas: 1st spraying – full emergence phase, 2nd – bud formation to beginning of flowering phase.

Ornamental bulbous flower crops (daffodils and tulips): 1st spraying – during the bud emergence phase, 2nd – 15–20 days after the first.

Immunocytophyte is used for spraying vineyards, apple trees, and currants during their growing season. To treat 50 m2 of vineyard, apple tree, or currant, dissolve two tablets in 30 ml (2 tablespoons) of cold water, stir after 20–30 minutes until completely dissolved, add 3 l of water to the solution for bushes and young trees, or 5 l of water for mature trees, and spray the plants with the resulting solution.

Grapes: 1st spraying – before flowering, 2nd – 10–12 days after the first, 3rd – 15–20 days after the second.

Apple tree: 1st spraying – bud differentiation to pink bud phase; 2nd – immediately after flowering; 3rd – during fruit set and fruit growth (10–30 days after the second).

Currants: 1st spraying – bud burst to beginning of flowering phase; 2nd – end of flowering phase; 3rd – 20–30 days after the second.

Use the aqueous solution of Immunocytophyte on the day of preparation. Do not spray during rain, before rain, or when dew is present. Must not be used in a mixture with potassium permanganate. In case of a potential epiphytotic situation (warm and humid weather) that facilitates the development of fungal and bacterial diseases, the plant must be treated with a fungicide 2 weeks after the last Immunocytophyte treatment.

Camposan M (aqueous solution) is used to prevent crop lodging. To this end, winter rye is treated in the heading phase with a 0.8–1% solution of the preparation for ground spraying and a 2.4–6% solution for aerial spraying, and winter barley is treated 10 days before the start of the heading phase with a 0.23–0.5% and 1.4–4% solution, respectively.

Camposan M (aqueous solution) + chlormequat chloride (60% aqueous solution) is used to prevent crop lodging. Application methods include ground and aerial spraying. The application rates are 1.5–2 + 3–3.3 l/ha for winter rye during the stem elongation phase, 1–2 + 3–5 l/ha for winter wheat from the beginning of stem elongation to the middle of the stem elongation phase, and 1–2 + 3 l/ha for winter barley 10–12 days before the start of the heading phase.

Crotonolactone is a reddish-yellow liquid with a 50% content of the active ingredient 2-buten-4-olide-oxo-2,5-dihydrofuran. It is soluble in water, benzene, ethanol, and ether. It is recommended for pre-sowing seed treatment and spraying of growing plants.

Quartazine is a 95% crystalline powder that is highly soluble in water. The active ingredient of this preparation is dimethyl(2-chloroethyl)hydrazinium chloride. The preparation is easily absorbed and rapidly transformed within plants. It is recommended for pre-sowing seed treatment and spraying of growing plants.

Megafol is a liquid biostimulant produced from plant amino acids containing prohormonal compounds. Its components are obtained through enzymatic hydrolysis of high-protein plant substrates.

The application of Megafol provides balanced plant nutrition. When combined with foliar top dressing, it enhances the effect of fertilizers, acting as a transport agent. It is also essential for overcoming stress when using pesticides. Megafol stimulates metabolism and other processes occurring in plants. The composition includes: amino acids – w/w 28.0%, organic nitrogen – w/w 4.5%, soluble potassium – w/w 2.9%, organic carbon – w/w 15.0%

Megafol is used for various crops:

Fruit and berry crops: (grapes, apples, pears, strawberries, raspberries, peaches, citrus, olives, apricots, tropical fruits): 250–350 ml/hl before flowering, and also during fruit set and fruit development.

Vegetable crops: (tomatoes, sweet peppers, eggplants, courgettes, cucumbers, leafy vegetables, etc.): 250–350 ml/hl in open soil, 150–200 ml/hl in greenhouses, applied every 10–15 days after planting.

Cereals, grain legumes, and maize: 0.5–1.5 l/ha (tillering – stem elongation + heading).

Industrial crops: (sunflower, soybean, tobacco, sugar beet, rapeseed, cotton) 1.0–2.0 l/ha.

Combinations of Megafol with mineral oils are not permitted. A combination of Megafol with copper-containing fungicides is acceptable only for use on grapes and tomatoes. Before treating plums, testing on a small number of trees of each cultivar is necessary. When combined with Blaster N, a ratio of 150+150 g/hl is recommended. When combined with fertilizers of the Master or Plantafol ranges, the application rate of Megafol is 0.15–0.5 l/ha.

The petroleum growth substance is the sodium salt of naphthenic acids. Under the influence of the preparation, the germination energy and seed germination, as well as plant growth and productivity, are increased.

It is recommended for seed treatment of cereal crops, which is carried out immediately before sowing with a 0.01% aqueous solution using the semi-dry method – 10 l of working solution per 1 t of seed material.

Oriz is a 0.6% granular preparation. It has a retardant effect on rice. The active ingredient is paclobutrazol. Oriz has low toxicity to warm-blooded animals. The LD50 of the preparation for rats is 1500 mg/kg. The preparation is non-flammable, non-explosive, does not cake, and does not cause corrosion. The storage life of Oriz is 2 years.

Oriz at a dose of 30 kg/ha is applied to rice in the stem elongation phase.

Biostimulants for root development, immunity, and fruit quality

To accelerate the survival rate of transplants and overcome transplanting stress, an agronomist needs specialized root stimulators. The liquid preparation Radifarm activates the development of lateral and adventitious roots, helping plants recover from temperature shocks or excessive soil moisture and humidity. Rapid absorption of water and nutrients triggers early photosynthesis, which shortens the total growing season of crops.

The composition of Radifarm includes:

• organic substances — 30.0% w/w;
• protein polypeptides — 11.0% w/w;
• polysaccharides — 7.00% w/w;
• free amino acids — 1.0% w/w;
• chelated iron — 0.20% w/w;
• chelated zinc — 0.20% w/w;
• steroidal glucosides — 0.2% w/w;
• vitamin complex — 0.04% w/w.

The preparation is applied via fertigation or irrigation according to the following schemes:

• Vegetable crops: 400–500 ml per 1000 m² during transplanting, repeat after 7 days — 200–300 ml per 1000 m². For irrigation, use a working solution at a rate of 100–300 ml of preparation per 100 l of water.
• Flowers: 400–500 ml per 1000 m² of soil at planting, after 7 days — 200–300 ml per 1000 m² of soil.
• Potted and ornamental plants: 2–3 applications with an interval of 7 days after potting, the dosage is 2.5 ml/m³ of water.
• Fruit and forest trees: 200–300 ml of ready-made solution per single plant at planting.

In the final stages of the growing season, to improve the marketability of products, the biostimulant Sweet is used. The preparation is a concentrated solution of mono-, di-, tri- and polysaccharides (25.0% w/w), uronic acids (0.2% w/w), meso-elements (11.0% w/w), and boron (0.23% w/w). There are no synthetic hormones in the composition. Applications accelerate ripening, increase fruit sugar content, and improve their coloration and shelf life during transport.

Crop	Application rate and timing
Apple, pear	0.5–1.0 l/ha when fruit coloring appears, then 0.5–1.0 l/ha 20 days before harvesting
Stone fruits	0.5–1.0 l/ha when fruit coloring appears, then 0.5–1.0 l/ha 10–15 days before harvesting
Grapes	0.5–1.0 l/ha when fruit coloring appears, then 0.5–1.0 l/ha 20 days before harvesting
Tomatoes	0.5–1.0 l/ha when fruit coloring appears
Pepper, eggplants	0.5–1.0 l/ha 7–10 days before harvesting
Flowers	200–300 ml per 100 l of water when the bud opens
Watermelon, melon	0.5–1.0 l/ha after fruit formation and again after 10–15 days
Strawberry	0.5–1.0 l/ha after the berry turns white and again after 8–10 days
Sugar beet	0.5–1.0 l/ha during the active growth period of the root crop

The application rates of Swit are calculated based on a standard working solution consumption: 1000 l/ha for orchards and vegetables, and 200 l/ha for field crops. The efficacy of the product increases when used in combination with the Megafol stimulant at a dose of 0.2–0.3 l/ha.

For integrated protection against abiotic stresses and fungal diseases, the natural growth regulator Silk is used. The active ingredient of the product is triterpene acids (chemical formula C30H46–48O4), extracted from the needles of Siberian fir. On the market, the product is available in four forms: Silk VE (50 g/l), Silk TAB (100 g/kg), Silk P (100 g/kg), and Silk G (100 g/kg).

Triterpene acids break seed dormancy, stimulate cell elongation in roots, coleoptiles, stems, and leaves. In plants during the growing season, terpenoids enhance transpiration through stomatal regulation and increase the intensity of photosynthesis by accelerating photosynthetic phosphorylation in chloroplasts.

Specific retardants for rice paddies

In rice cultivation, it is critically important to prevent crop lodging before harvesting. For these purposes, specialized products with retardant action are used — Celtard and Sumadic. They inhibit excessive linear growth of the stem, redirecting plant resources to grain formation.

The product Celtard is produced in the form of a 6% yellowish-brown or colorless odorless crystalline powder. It has low toxicity to warm-blooded livestock animals (LD50 for rats is 5000 mg/kg), is non-explosive, and does not cause equipment corrosion. The product dissolves well in organic solvents (acetone and methanol) but is poorly soluble in water.

The product Sumadic is a 0.04% granular formulation based on the active ingredient uniconazole. It is not prone to caking, is non-flammable, non-explosive, and chemically neutral to metals. The product also belongs to the category of low-hazard substances (LD50 for rats — 2000 mg/kg).

• Dosage of Celtard on rice — 2.5 kg/ha
• Dosage of Sumadic on rice — 30 kg/ha
• Application timing for both retardants — stem elongation stage
• Melting point of Celtard — 210 °C

Fusicoccin and chlormequat chloride: managing stem strength and root formation

Fusicoccin is a highly active metabolite of a phytopathogenic fungus used in crop production as a growth regulator. In its chemical structure, it is a glycoside of a carbotricyclic diterpene with a molecular weight of 680 and a gross formula of C₃₆H₅₆O₁₂. Even in ultra-low concentrations, the product demonstrates a pronounced physiological effect. It actively stimulates seed germination, accelerates the growth of vegetative organs, and induces root formation in cuttings.

• Working concentration of fusicoccin — 10⁻¹⁶–10⁻⁴ M

Chlormequat chloride (CCC, or (2-chloroethyl)trimethylammonium chloride) is used to prevent crop lodging. It is a white crystalline hygroscopic substance with a molecular weight of 158.1 and a melting point of +245 °C, which easily dissolves in water and polar solvents. In aqueous solutions, the product completely dissociates into chlorine ions and β-chloroethyltrimethylammonium. The product acts as a retardant, inhibiting cell elongation in the subapical meristem.

Under the influence of chlormequat chloride, profound anatomical changes occur in the stem at the level of the lower internodes. The cavity of the straw is almost completely filled with parenchyma tissue, the number of vascular bundles increases, and the content of cellulose and lignin rises. This significantly increases the specific weight of mechanical tissues, making the stem strong and resistant to breaking. For green crops, spraying is carried out strictly according to the regulations.

• Application timing — stem elongation stage
• Rate for short-stature cultivars — 4 kg/ha a.i.
• Rate for tall-stature cultivars — 6–8 kg/ha a.i.
• Water consumption (ground) — 100 l/ha
• Water consumption (aerial) — 25 l/ha

Zircon and Epin-extra: protection against stress and immune stimulation

Zircon is produced from natural plant raw materials, creating a complex product with the functions of a growth regulator, root-forming agent, and inducer of flowering and disease resistance. Application of the product accelerates the growth and development of crops by 5–10 days, increases yield by 35–60 %, and improves produce quality. Zircon increases the adaptive capacity of plants, protecting them from frost, drought, excess humidity, and light deficiency. It also stimulates fruit set and root formation, accelerates the flowering of ornamental plants, and reduces the accumulation of heavy metals.

Zircon treatment significantly reduces the susceptibility of plants to common diseases. The product is effective against potato and tomato late blight, potato and apple scab, bacteriosis and fusarium wilt of vegetable and flower crops, strawberry gray mold, and powdery mildew on roses and blackcurrants. Zircon belongs to hazard class IV, meaning it is practically harmless to humans, warm-blooded animals, fish, and bees. It does not exhibit phytotoxicity, does not accumulate in the soil, and does not contaminate surface or groundwater.

Crop	Application rate	Method, treatment timing, and working solution consumption
Potato	0.5 ml/l of water	Pre-sowing tuber treatment. Consumption — 1 l per 100 kg
	0.33 ml/l of water	Spraying plants at the full emergence phase and the beginning of the budding phase. Consumption — 3 l per 100 m²
Cucumber	0.22 ml / 200 ml of water	Seed soaking for 8 hours. Consumption — 200 ml per 200 g
	1 ml / 10 l of water	Spraying plants at the budding phase. Consumption — 3 l per 100 m²
Tomato	1.25 ml / 100 g	Seed soaking for 1 hour. Consumption — 150 ml per 100 g
Pepper	0.04–0.06 ml / 100 ml of water	Seed soaking for 2 hours. Consumption — 100 ml per 100 g
	1 ml / 10 l of water	Spraying plants at the flowering phase. Consumption — 3 l per 100 m²
Cabbage	0.25 ml / 10 l of water	Spraying plants at the head formation phase. Consumption — 4 l per 100 m²
Carrot	0.13 ml / 10 l of water	Spraying plants at the bunch ripeness phase (8–10 leaves). Consumption — 3 l per 100 m²
Pea	0.04 ml / 100 ml of water	Pre-sowing seed treatment. Consumption — 100 ml per kg
	0.3 ml / 10 l of water	Spraying plants at the budding phase. Consumption — 3.5 l per 100 m²
Apple	0.1 ml / 100 ml of water	Cuttings soaking for 18 hours. Consumption — 100 ml per 20 cuttings
	1 ml / 10 l of water	Spraying at the budding phase. Consumption — 5–10 l per tree
Sweet cherry	2.5 ml / 10 l of water	Spraying at the budding phase. Consumption — 5–10 l per tree
Cherry	0.5 ml / 1 l of water	Cuttings soaking for 18 hours. Consumption — 100 ml per 20 cuttings
	2.5 ml / 10 l of water	Spraying at the budding phase. Consumption — 5–10 l per tree
Plum	0.02 ml / 100 ml of water	Cuttings soaking for 18 hours. Consumption — 100 ml per 20 cuttings
Cherry plum	2.5 ml / 10 l of water	Spraying at the budding phase. Consumption — 5–10 l per tree
Strawberry	0.3 ml / 10 l of water	Spraying at the budding phase. Consumption — 3 l per 100 m²
Currant	0.4 ml / 10 l of water	Spraying at the budding phase. Consumption — 4 l per 100 m²
Rose	0.02 ml / 100 ml of water	Cuttings soaking for 4 hours. Consumption — 100 ml per 20 cuttings
	1–2 ml / 10 l of water	Spraying at the beginning of shoot growth. Consumption — 4 l per 100 m²
Chrysanthemum	1 ml / 1 l of water	Spraying before bud formation. Consumption — 1 l per 30 m²
Pear	0.05 ml / 200 ml of water	Cuttings soaking for 18 hours. Consumption — 200 ml per 40 cuttings
Thuja, spruce	0.05 ml / 100 ml of water	Cuttings soaking for 14 hours. Consumption — 100 ml per 10 cuttings

The product Epin (Epin-extra) is a natural plant growth regulator with pronounced anti-stress properties. It strengthens the plant's own immunity, helps transplants root faster during prick-out, and minimizes stress during planting. Epin is effective both at the seed material preparation stage (soaking seeds and bulbs) and during the growing season (spraying during the budding and flowering phases).

Epin-extra provides a wide range of positive effects on crops:

• acceleration of seed germination and high-quality rooting of transplants during prick-out and planting;
• reduction of maturation periods and increase in the total harvest;
• protection of plants from late frosts and other adverse environmental factors;
• increased resistance to late blight, scab, fusarium wilt, and bacteriosis;
• active lateral shoot development, contributing to the rejuvenation of old and recovery of weakened plants;
• neutralization of nitrates, radionuclides, and heavy metals in the finished produce.

Application: pre-sowing or pre-planting treatment. Seeds of vegetable crops are soaked in an Epin-extra solution (1–2 drops per 100 ml of water for tomatoes, cucumbers, peppers, and eggplants) for 18–20 hours at a temperature of 20 °C. Seeds of flower crops – 4 drops of Epin-extra per 100 ml of water for 18 hours. Flower bulbs and cuttings are soaked before planting in an Epin-extra solution (1 ml per 2 l of water) for 24 and 12 hours, respectively. Potato tubers are sprayed before planting (1 ml per 250 ml of water per 50 kg of potato tubers).

Spraying of plants during the growing season. Dissolve 1 ml of Epin in 5 l of water and mix thoroughly. Perform spraying by wetting the leaves evenly. Use the working solution on the day of preparation, avoiding any alkaline reaction of the solution. Apply treatment to plants during the following phases: potatoes, tomatoes – budding – beginning of flowering; root crops – upon emergence; cucumbers – at the 2–3 true leaf stage with repetition in the budding phase; peppers – at the beginning of budding with repetition in the flowering phase; tulips – upon bud appearance; fruit and berry crops – in the budding phase with repetition after 20 days. The application rate of the working solution is 2–5 l per young tree and 5–8 l per mature one. Under stressful growing conditions (lack of light, frosts, diseases), perform spraying every 7–10 days until the signs of disease in plants disappear completely.

Ethylene is a natural plant development regulator; it forms in plant tissue during specific phases of the growing season and promotes fruit ripening, alters respiration intensity and enzyme activity. When applied externally (exogenously), it also promotes faster fruit ripening, causes leaf yellowing and defoliation.

Ethylene is a gas with a sweetish odor that burns with a luminous flame. It forms an explosive mixture with oxygen and air. The limits of explosive concentrations in the air are 3–34 volume percent. As a growth regulator, it is used in hermetic chambers, where it is supplied once a day in an amount sufficient to ensure a concentration in the air of 1:2000 – 1:5000 by volume. Green or unripe fruits are placed in the chamber and kept there for 2–3 days in the presence of ethylene at a temperature of 18–22 оС and a relative humidity of at least 85 %. Treatment of fruits with ethylene does not affect their taste and nutritional qualities.

Ethrel is a preparation of American manufacture, based on 2-chloroethylphosphonic acid (phosphonate). It is used as a growth inhibitor, defoliant, and stimulant for fruit ripening and fruit abscission. Each liter of Ethrel contains 480 g of the active ingredient. When sprayed as an aqueous solution onto the plant surface, it is absorbed completely within 24 hours, and 75 % within the first 2–3 hours. In plant tissues, Ethrel decomposes into hydrochloric acid, phosphoric acid, and ethylene, which exerts a physiological effect on the plant.

Ethrel is a liquid with strongly pronounced acidic properties. At a pH above 4, the preparation begins to decompose; therefore, when working with it, avoid contact with alkalis, and solutions should be prepared immediately before use. When treating with the preparation, it is recommended to wet the plant well, for which about 1000 l/ha of solution is used at a concentration of no more than 0.07–0.1 %.

Succinic acid is one of the most effective biogenic growth regulators. It plays an important role in plant metabolism, forming in a free state in the organism during the decomposition of isocitric acid and the oxidative conversion of ketoglutaric acid. One of the mechanisms of the positive influence of succinic acid on plant life activity is considered to be the stimulation of respiration, the intensity of which determines the metabolic level of the plant organism.

To obtain succinic acid, bacterial fermentation of ammonium tartrate or calcium malate is usually used. As a by-product, succinic acid is obtained from the distillation of amber waste. Synthetic succinic acid is obtained from dibromoethane via the corresponding dicyanide, as well as by catalytic reduction of maleic or fumaric acids. A method has been developed for obtaining succinic acid from furfural waste (still bottoms) of hydrolysis plants of furan compounds. Furfural is obtained from cotton ginning waste (guza-paya) and cotton husks, as well as from sunflower stalks. Succinic acid obtained from this waste contains 2 % fumaric acid. The mixture of succinic and fumaric acids is not inferior in its effect on the plant to pure succinic acid.

Succinic acid is used in concentrations of 0.001–0.01 % for seed treatment before sowing. Such treatment stimulates seed germination and plant growth.