The role of vitamins in the life activity of plants and agricultural produce

How vitamins influence plant vital activity

Vitamins are low-molecular organic compounds that coordinate key physiological processes. Unlike humans and livestock animals, plants are capable of synthesizing almost all the vitamins they need on their own. Upon entering plant tissues, these substances transition into the active form of coenzymes and integrate into enzyme systems. Without their participation metabolism slows down, and the development of the organism comes to a halt.

In crop production, the vitamin content in the finished product determines its feed and nutritional value. A deficiency or excess of these elements in feed leads to metabolic disorders in livestock animals. In the absence of vitamins in the diet, severe pathologies develop, potentially leading to the loss of livestock. Each group of compounds is responsible for specific metabolic processes in living organisms:

• breakdown of carbohydrates and release of energy — vitamins B1, B2, PP;
• regulation of amino acid synthesis and protein metabolism — vitamins B6, B12;
• breakdown and synthesis of fatty acids and fats — vitamin B3;
• synthesis of purine and pyrimidine bases, nucleic acid metabolism — vitamins B9, B12;
• formation of acetylcholine, glutathione, and steroid hormones — specific groups of vitamins;
• development of integumentary tissues and embryos — fat-soluble vitamins A and E;
• formation of organism structures — vitamin D.

• Total known vitamins — about 30
• Obtained from food — 20
• Total known enzymes — about 800
• Function with the help of vitamins — about 200

The main reason for vitamin deficiency in consumers of agricultural produce is an unbalanced diet or technological losses during storage and processing of raw materials. Deficiencies are also caused by the suppression of beneficial intestinal microflora, genetic metabolic disorders, and increased physiological demand during unfavorable climate conditions. This is characteristic of both humans and livestock animals.

All vitamins are divided into fat-soluble and water-soluble. Their chemical structure underlies their names, but in practice, letter designations are often maintained. Most of them are thermostable and resistant to external influences.

Vitamin group	Chemical class	Representatives
Fat-soluble	Carotenoids	Vitamin A
Fat-soluble	Steroids	Vitamin D
Fat-soluble	Heterocycles	Vitamin E
Fat-soluble	Aromatic substances	Vitamin K
Fat-soluble	Unsaturated fatty acids	F-group complex
Water-soluble	Carbohydrates	Vitamin C (ascorbic acid)
Water-soluble	Heterocycles	B-group vitamins (B1, B2, B6, B12), biotin, nicotinic and folic acids
Water-soluble	Aliphatic compounds	Pantothenic acid (B3)

Vitamin A synthesis and the role of carotenoids in photosynthesis

Pure vitamin A is not produced in plant tissues. It is present in the form of four individual representatives: retinol, retinyl acetate, retinal, and retinoic acid. These compounds have two vitamers — A1 and A2 (A2 has an additional double bond in the β-ionone ring), which are structurally 20-carbon polyprenyl alcohols. They are formed directly in the consumer's organism from plant carotenoids: α-, β-, and γ-carotenes.

β-carotene, which contains two β-ionone rings, possesses the highest biological activity. Upon hydrolytic breakdown by the enzyme carotene dioxygenase, one of its molecules produces two molecules of retinol. Thanks to the double bonds in the molecule, the substance actively participates in redox reactions, forming peroxides and accelerating the oxidation of other compounds.

In plants themselves, carotenoids perform the role of an essential component of the light-harvesting pigment complex. They are responsible for the primary absorption of light and the inter-pigment transfer of electromagnetic energy. This allows the plant to precisely regulate the energy saturation of chlorophyll and maintain a high intensity of photosynthesis.

Carotene accumulation in crops and its influence on product quality

For an agronomist, the value of commodity crops is determined not only by yield but also by the quality of the produce, specifically the content of carotene (provitamin A). The accumulation of carotene in forage crops directly affects livestock production: in summer, with an abundance of fresh grass, milk and butter are rich in vitamin A, whereas in winter their vitamin value decreases sharply. In the human and animal organism, this yellow pigment is converted into vitamin A, participating in the formation of visual pigments together with opsin proteins, regulating bone growth, and maintaining the integrity of epithelial tissues.

A lack of vitamin A leads to A-avitaminosis, which manifests as "night blindness" (impaired night vision), dryness of the eyeballs, fine skin rash, loss of hair shine, and hair loss. Deficiency of this element is critical for people working night shifts: bus, trolleybus, tram, and taxi drivers, as well as electric locomotive engineers. However, an excess of retinol is also harmful — it causes weakness, decreased performance, reduced immunity to colds and infections, loss of appetite, and liver enlargement.

Vitamin A content is expressed in international units (IU), where 1 IU equals 0.6 mcg of pure β-carotene (1 mcg = 0.001 mg). One gram of pure carotene is equivalent to 1,670,000 IU, and one gram of pure vitamin A1 is equivalent to 3,300,000 IU. Ionones — unsaturated ketones of the cyclohexene series — occupy an important place in the structure of these compounds.

• Daily requirement for an adult — 1.0 mg
• Requirement for pregnant women — 1.25 mg
• Requirement for nursing mothers — 1.5 mg

Product	Vitamin A (carotene) content, mcg/g
Vegetable oils	0
Potato	0
Wheat, wheat flour, bread	0–0.2
Meat and poultry	0.04
Fish	traces
Summer milk	1
Butter	12
Apricots	20
Tomatoes	20
Lettuce and spinach	25–50
Red carrot	90
Alfalfa leaves	100
Cod liver oil	300
Shark liver oil	750
Rockfish liver oil	900
Sperm whale liver oil	60000

Physiological significance of vitamin B1 for plants and humans

In the plant organism, B-group vitamins — including B1 (thiamine), B2 (riboflavin), PP (nicotinic acid), B6 (pyridoxine), B9 (folic acid), and B12 (cyanocobalamin) — perform essential regulatory functions. A special role is played by water-soluble vitamin B1 (thiamine, or aneurin), which contains sulfur in its molecule and is a derivative of pyrimidine and thiazole. It acts as an essential participant in carbohydrate metabolism and plant cellular respiration.

Thiamine is a component of the coenzyme carboxylase (an enzyme of alcoholic fermentation), which is an ester of thiamine and pyrophosphoric acid. In the form of thiamine pyrophosphate, it acts as a coenzyme for pyruvate decarboxylase — a key enzyme that catalyzes the decarboxylation of pyruvic acid (CH3—COCOOH), which is formed during glycolysis. Thiamine is also a component of the enzyme complex that catalyzes the oxidative decarboxylation of keto acids (for example, α-ketoglutaric acid) in the Krebs cycle reactions.

For humans and livestock animals, thiamine serves as an important stimulant for the nervous, muscular, and digestive systems, participating in protein and lipid metabolism. Its deficiency leads to muscle weakness, leg pain, decreased concentration, and irritability. Acute hypovitaminosis leads to polyneuritis (beriberi disease), which occurs with prolonged monotonous diets consisting of cereals stripped of their outer husks or polished rice. Since vitamin B1 is concentrated precisely in the husks, harvesting technology directly affects the nutritional value of products.

Vitamin value of crop production and human requirements

The quality of the harvested crop is assessed not only by its volume but also by its biological value to the consumer. B-group vitamins, which accumulate in the commercial parts of plants, directly determine the nutritional value of the products. For instance, vitamin B1 (thiamine) deficiency often manifests in diseases of the gastrointestinal tract, liver, prolonged fevers, and in women during pregnancy and lactation. A well-balanced diet based on vegetable, grain, and grain legume crops allows for effectively compensating for this shortage.

The main plant sources of thiamine are potato, sweet red pepper, green peas, sorrel, onion, carrot, cauliflower, tomatoes, soy, beans, and nuts. High concentrations of the vitamin are also found in various grain and legume crops. It is important for an agronomist to be oriented in the actual content of these substances in the grown crops to control the quality of the resulting produce.

• Daily adult requirement for B1 — 1.5 mg
• Requirement for B1 during pregnancy and lactation — 1.8–2.3 mg
• Daily adult requirement for B2 — 1.5–3.0 mg

Physiological role of vitamins B2, B3, and B5 in metabolism

Vitamin B2 (riboflavin) serves as an important structural element of the coenzymes FMN and FAD, which ensure hydrogen transfer in redox processes. This vitamin actively participates in carbohydrate and protein metabolism, and is also responsible for the normal functioning of the visual organs. A lack of riboflavin leads to sharp weight loss, cracks on the skin and lips, impaired vision, and slowed wound healing. The main plant sources of B2 are buckwheat, tomatoes, potato, carrot, cauliflower, green peas, and beans.

Vitamin B3 (pantothenic acid) is a component of coenzyme A, which activates and transfers acyl residues, and regulates the synthesis of fatty acids, citric acid, and sterols. In the case of pantothenic acid deficiency in humans and livestock animals, metabolism is disrupted, dermatitis develops, and hair loss occurs. This vitamin is widespread in nature, and its main sources are grain crops, potato, tomatoes, cauliflower, and legumes.

Vitamin B5 (PP), represented by nicotinic acid and nicotinamide, prevents the development of a dangerous disease — pellagra. Its derivatives, NAD and NADP, participate in biological oxidation, glycolysis, and the tricarboxylic acid cycle. In tissues, the NAD content is usually 5–10 times higher than that of NADP. Niacin deficiency leads to fatigue, insomnia, skin peeling, and ulcers on mucous membranes, and its presence in feed is critically important for the assimilation of plant protein.

The concentration of vitamins in various crops varies significantly. The table below provides detailed data on the content of B-group vitamins, as well as vitamins E and H, in major agricultural crops.

Crop	B1	B2	B3	B6	B9	E	H	Additional indicators of vitamin accumulation
Cabbage	150	70	200	120	100	40	20	2	3	15	0,6	20	95
Lettuce	100	300	100	150	45	500	0,2	0,2	900	—	—	—	—
Spinach	100	300	170	100	20	50	200	6	4	0,1	0,8	500	2.7
Tomatoes	100	400	60	70	30	4	1	0,1	700	46	—	—	—
Cucumbers	40	50	150	9	2	0,16	200	—	—	—	—	—	—
Apples	50	20	8	26	18	1	0.08	100	24	—	—	—	—
Pears	70	30	5	0,2	—	—	—	—	—	—	—	—	—
Plums	120	20	10	0,8	300	—	—	—	—	—	—	—	—
Apricots	60	40	9	6000	—	—	—	—	—	—	—	—	—
Cherries	50	15	400	—	—	—	—	—	—	—	—	—	—
Oranges	90	40	340	80	80	53	2	30	0,03	100	210	—	—
Blackcurrant	150	1000	—	—	—	—	—	—	—	—	—	—	—
Grapes	50	20	10	10	20	3	70	12	—	—	—	—	—
Wheat	350	80	1380	430	190	910	5	0,05	6	20	170	—	—
Corn	580	100	500	340	20	6	0,05	3,5	45	—	—	—	—
Peas	520	260	380	300	430	3200	9	2	250	—	—	—	—
Radish	110	30	23	0.3	—	—	—	—	—	—	—	—	—
Carrots	100	50	350	130	100	5	1200	3	2	75	0.8	12000	48
Potatoes	100	50	400	20	80	21	0,6	0,1	1.0	29	—	—	—

Nitrogen metabolism and cell strength: the role of vitamins B6, B8, and B9 in plants

Harvest quality directly depends on nitrogen metabolism in plant tissues. Vitamin B6 plays a key role in these processes, combining three active ingredients: pyridoxine, pyridoxal, and pyridoxamine. In the form of pyridoxal phosphate, it is part of enzymes that catalyze the transamination, decarboxylation, and racemization of amino acids. A deficiency of this vitamin blocks protein biosynthesis, which leads to stunted plant growth, and in humans and animals, it causes anemia, dermatitis, and seizures.

Vitamin B8 (the active form is myo-inositol) is responsible for the structural strength of tissues and the accumulation of nutrients. It acts as a precursor to uronic acids, which form plant cell walls, and also participates in the synthesis of fats and membrane lipids. By combining with phosphoric acid, myo-inositol forms phytin — a calcium-magnesium salt that serves as the main phosphorus reserve in seeds. Inositol deficiency in the human diet leads to fatty liver, nervous system dysfunction, and contributes to the development of atherosclerosis.

Vitamin B9 (folic or pteroylglutamic acid, folacin) is necessary for plants for cell division and carbon metabolism. Working as a coenzyme, it ensures the transfer of single-carbon fragments during the biosynthesis of purine bases, methionine, and serine. Without a sufficient amount of folacin, DNA and RNA reproduction is disrupted, as well as protein synthesis in plant tissues. For humans, a deficiency of this vitamin is dangerous due to the development of malignant "tropical" anemia and a reduction in the body's resistance to diseases.

Nutritional value of produce: from nutrient balance in the field to human health

When planning the crop structure, it is important to consider the amino acid composition of crops, as it directly affects consumer health. The human need for niacin (vitamin PP) is partially met through its synthesis from tryptophan, where 1 mg of niacin is formed from 60 mg of the amino acid. If the diet is dominated by crops with a low content of this amino acid, a serious vitamin deficiency develops in the population.

Cobalt requires special attention as a micronutrient necessary for the synthesis of vitamin B12 (cobalamin, cyanocobalamin). This vitamin is produced exclusively by microorganisms, and its active forms — methylcobalamin in the cell cytoplasm and deoxyadenosylcobalamin in the mitochondria — participate in hydrogen transfer, the creation of new carbon bonds, and the metabolism of methylmalonic acid. The accumulation of the vitamin in the human liver and its synthesis by intestinal microflora are impossible without sufficient intake of cobalt with food.

To assess the quality of the harvested produce, an agronomist needs to be guided by recommended vitamin intake levels and their concentration in crops. Proper selection of cultivars and growing conditions allows for the targeted improvement of the vitamin value of grain, vegetables, and fruits. The balanced diet of consumers directly depends on the mineral and vitamin composition of the produce harvested from the fields.

Vitamin	Daily requirement for an adult	Dietary sources
B5 (Pantothenic acid)	15–20 mg (20–25 mg under high physical and nervous/emotional stress)	Wheat flour, buckwheat and barley groats, cereal bran, bakery and grain products, beans, peas, kidney beans, soy, lentils, red pepper, potatoes, white cabbage, rowan berries, as well as meat and dairy products, liver, kidneys, fish, eggs.
B6 (Pyridoxine)	2–3 mg	Wheat germ, beans, peas, peanuts, fresh green pepper, potatoes, white cabbage, carrots, tomatoes, as well as yeast, liver, meat, fish, eggs, milk, cheese.
B8 (Inositol, myoinositol, mesoinositol)	0.5–1.5 mg	Wheat grain, green peas and dried peas, green beans, cauliflower and white cabbage, potatoes, beet, onion and scallions, tomatoes, carrots, oranges, apples, pears, peaches, melon, strawberries.
B9 (Folic acid, folacin)	0.2 mg (twice as much during pregnancy and breastfeeding)	Green leafy vegetables (spinach, lettuce, parsley greens), cabbage and cauliflower, beans, beet, potatoes, tomatoes, apples, grapes, lemons, wheat, rye, as well as liver, heart, yeast.
B12 (Cobalamin, cyanocobalamin)	2.5–5.0 mcg	Liver (100 mcg per 100 g of liver), kidneys, egg yolks, fish, milk. It is absent in plants and is synthesized by microflora provided that cobalt is present.

Accumulation of B-group vitamins and choline in crops

Vitamin B13 (orotic acid) stimulates the growth of the organism and actively participates in protein metabolism. In plant cells, it stimulates the synthesis of nucleotides, which are components of nucleic acids. In nature, this substance accumulates in yeast and is also found in the liver of livestock animals.

Vitamin B15 (pangamic acid) is found in all plant-based foods. It participates in transmethylation processes as a donor of methyl groups, activates redox processes, and promotes the accumulation of macroergic compounds. In the human body, this vitamin increases tolerance to oxygen starvation, neutralizes toxic substances, stimulates the functioning of the pituitary and adrenal glands, and prevents fatty liver. The daily requirement for pangamic acid is about 2 mg.

Choline (choline chloride), with the chemical formula (CH3)3—N+(OH)-—CH2—CH2OH, is a component of the phospholipid phosphatidylcholine. It acts as a donor of methyl groups in transmethylation reactions and participates in the synthesis of phosphatides, acetylcholine, methionine, adrenaline, and nucleic acids. Choline deficiency in livestock animals leads to fatty liver degeneration and internal hemorrhages. Valuable sources of choline among agricultural crops include rice, oats, barley, corn, wheat germ, and soybeans, as well as spinach and white cabbage. The daily human requirement for choline is 500–1000 mg.

Ascorbic acid and provitamins D in plant production

Vitamin C (ascorbic acid) is a group of water-soluble compounds, derivatives of L-gulonic acid. In redox reactions, it functions as a hydrogen donor: by donating two hydrogen atoms, ascorbic acid converts into dehydroascorbic acid (the reverse process occurs with the participation of the enzyme dehydroascorbate oxidase, using glutathione hydrogen). The vitamin participates in plant cellular respiration, carbohydrate and amino acid metabolism, and increases their resistance to environmental stress factors. In plant material, the substance is present in the form of ascorbic and dehydroascorbic acids, as well as ascorbigen.

The human body cannot synthesize or store vitamin C, so its content in the harvest directly determines the nutritional value of the produce. Its main sources are tomatoes, scallions, parsley, cabbage, quince, cherry, black currant, lemon, orange, as well as sweet (bell) pepper and rose hips. The absolute record-holder is immature (green) walnut fruit, containing up to 3500 mg % of vitamin C, which is 50 times more than in citrus fruits. Due to the high share of consumption, potatoes remain an important source, although the concentration of the vitamin in them is lower. The daily requirement for vitamin C is 50–100 mg for men, 48–80 mg for women, 72 mg for pregnant women, and 80 mg for breastfeeding mothers.

Vitamin D (calciferol) consists of a group of fat-soluble compounds of the sterol series. Plants contain its provitamins — phytosterols (methylenecycloartenol, campesterol, sitosterol, stigmasterol), which, by their chemical structure, are monohydric unsaturated cyclic alcohols with a phenanthrene ring. Under the influence of ultraviolet radiation with a wavelength of 280–310 nm, phytosterols are converted in the human and animal body into active forms — ergocalciferol (D2) and cholecalciferol (D3). These compounds regulate the transport of calcium and phosphorus ions, ensuring bone mineralization, and their deficiency causes rickets in children under 3–4 years old and bone softening in adults. Fish and animal liver are the richest in this vitamin.

• Daily requirement for vitamin B15 — about 2 mg
• Daily requirement for choline — 500–1000 mg
• Vitamin C in unripe walnuts — up to 3500 mg %
• UV spectrum for vitamin D activation — 280–310 nm
• Men's requirement for vitamin C — 50–100 mg/day
• Women's requirement for vitamin C — 48–80 mg/day

Product	Content
Cod liver oil	125
Animal liver	0.2—1.2
Butter (summer)	1—2
Butter (winter)	0.3—0.5
Milk	0.02—0.1
Egg yolk (winter)	3.5
Egg yolk (summer)	12.5
Vegetable oil	25—50
Brewer's yeast	12500—25000

Vitamin D is also found in fish oil, yeast, egg yolk, fatty cheeses, butter, milk, and eggs; it has been detected in certain plant-based foods (carrots, spinach, raspberries, lemons, sunflower seeds). The vitamin D content in food increases during the spring and summer periods and decreases in the autumn-winter season. A deficiency of vitamin D in the body is promoted by insufficient ultraviolet exposure, impairment of absorption processes in the intestine, and a decrease in the vitamin content in food. The minimum dose of vitamin D for children of different ages ranges from 0.0025 to 0.01 mg. The same dose can be recommended for pregnant women and nursing mothers.

Vitamin E (tocopherol) is a group of fat-soluble compounds derived from chromane; it brings together a group of seven tocopherol vitamins. Tocopherols regulate the intensity of free-radical reactions in living cells, prevent the oxidation of unsaturated fatty acids in membrane lipids, and influence the biosynthesis of enzymes.

A deficiency of this vitamin leads to disturbances in oxidative processes and mineral metabolism, especially calcium and phosphorus, as well as the sexual function of male and female organisms; muscle dystrophy develops. The most important property of vitamin E is its ability to increase the storage of fat-soluble vitamins in internal organs.

Vitamin E possesses antioxidant properties; it participates in the formation of intercellular substance, collagen and elastic fibers of connective tissue, and the smooth muscles of blood vessels and the digestive tract.

Vitamin E is contained mainly in green vegetables — lettuce, spinach, green peas, legumes, oat grain, wheat and corn germ, and also in very small quantities in animal tissues (liver). It is most abundant in vegetable fats, for example, corn, sunflower, soybean, cottonseed, and sea buckthorn oil; it is also present in milk, dairy products, and eggs. The daily requirement for the vitamin is 20-30 mg. A daily intake of 1.5-2 tablespoons of vegetable oil fully provides an adult with the daily dose of tocopherol.

Vitamin F (essential polyunsaturated fatty acids). The main ones among these acids are linoleic, linolenic, and arachidonic, which prevent the excessive accumulation of cholesterol in the walls of blood vessels.

A deficiency of this vitamin in the body leads to skin lesions: ulcers and necrosis form, and pigmentation changes; hair breakage and loss, as well as brittleness and splitting of nails, are observed. Vitamin F strengthens the body, contributes to the normalization of metabolism, delays the development of sclerotic processes, specifically prevents atherosclerosis, is effective in treating wounds and ulcers, increases the body's resistance to eczema and the effects of radioactive elements, and influences lactation and reproductive processes.

It is contained in butter, meat, and vegetable and animal fats. The daily requirement for the vitamin is 2000-4000 mg, for which it is sufficient to consume 20-30 g of any vegetable oil daily. Among vegetable oils, flaxseed, hemp, corn, soybean, cottonseed, and nut oils are the richest in this vitamin.

Vitamin H (biotin) is a water-soluble vitamin that acts as a coenzyme for carboxylase and participates in the biosynthesis of dicarboxylic organic acids from monocarboxylic acids.

A deficiency of vitamin H in the body causes disturbances in the metabolic processes of human skin: dermatitis, eczema, and seborrhea. It participates in fat metabolism and regulates the nervous system. Sources: milk, meat, eggs; among plant-based foods, vitamin H is abundant in wheat, rice, soybeans, young bean pods, peanuts, almonds, walnuts, fruits of black currant and raspberries, tea, green peas, tomatoes, green onions, potatoes, and cauliflower. The daily requirement for the vitamin is 0.15-0.30 mg.

Vitamin K (phylloquinone, vikasol) is a group of fat-soluble compounds derived from naphthoquinone; it functions as an electron carrier in the respiratory chain.

In the absence of vitamin K in the diet or if its absorption and assimilation by the body are impaired, bleeding occurs. The vitamin participates in blood clotting processes — it is essential for the formation of prothrombin and for the conversion of the latter into thrombin (it is no coincidence that vitamin K got its name from the Latin word "coagulatio," which means "blood clotting"). Animal products contain vitamin K2, while plant products contain K1 (2-methyl-3-phytyl-1,4-naphthoquinone), which is converted into vitamin K2 in the human and animal body.

Vitamin K1 is found in lettuce, parsley, spinach, cabbage and kale, carrots, potatoes, tomatoes, soybean oil, legumes, liver, and nuts. The highest content of this vitamin has been noted in rose hips, nettle leaves, and alfalfa. Animal-derived products, except for liver, contain insignificant amounts of vitamin K. In addition to food, sources of vitamin K include bacteria that produce it in the human intestine. The daily requirement of the human body for this vitamin is 0.2-3.0 mg.

Medicine from the garden bed: biological value of lesser-known vitamins in produce

Crop harvest quality is determined not only by standard indicators of proteins, fats, and carbohydrates, but also by the concentration of biologically active substances. Plants serve as the sole source of vitamins for humans and livestock animals, therefore, managing their accumulation in the field is a direct task of the agronomist. In addition to basic vitamins, crops synthesize a group of rare but vital compounds.

Vitamin P (rutin) regulates redox processes, in particular during the oxidation and reduction of ascorbic acid and adrenaline, and also controls the permeability of blood vessel walls. Its deficiency leads to capillary fragility and rapid fatigue. The highest concentration of bioflavonoids has been found in red chili peppers, rose hips, buckwheat, garden sorrel, leaf parsley, celery, carrots, beet, white cabbage, plums, black chokeberry, blackcurrant, red wine, citrus fruits, persimmons, and tea. For the pharmaceutical industry, vitamin P preparations are produced: citrin (from lemon juice), catechins (from green tea and citrus fruits), and rutin (from tea leaves, buckwheat, and Japanese pagoda tree). The daily human requirement for vitamin P is 25–35 mg.

Vitamin U (methylmethionine sulfonium chloride) represents an activated form of methionine. It stimulates the healing of the digestive tract mucous membranes, participates in the synthesis of choline and creatine, improves fat metabolism, as well as cerebral and coronary circulation. The main plant source of this anti-ulcer factor is white cabbage (especially its juice), as well as celery, beet, tomatoes, green tea, and fresh vegetable juices.

Lipoic acid normalizes carbohydrate metabolism by participating in the conversion of pyruvic acid to coenzyme A, and also regulates the metabolism of proteins, fats, and cholesterol. It prevents fatty liver and serves as an indispensable growth factor for microorganisms, including lactic acid bacteria. Furthermore, the acid has a detoxifying effect by binding heavy metal salts (mercury, lead, cadmium). Among plant products, rice and white cabbage are particularly rich in it. The daily human requirement for lipoic acid is 1.0–2.0 mg.

A special role in metabolism is played by vitamin Q, para-aminobenzoic acid (PABA), and carnitine. Vitamin Q (ubiquinone) is a quinone derivative with methoxyl groups in the ring and an isoprenoid side chain made of isoprene residues. It transports electrons between flavoproteins and cytochrome during cell respiration and is synthesized by plants from tyrosine or phenylalanine. PABA is necessary for the thyroid gland to function and accumulates in yeast, wheat germ, and spinach. Carnitine, which transports fatty acids into the mitochondria, is synthesized in the body from lysine, for which plant protein also serves as a source.

Managing biosynthesis: how mineral nutrition affects the vitamin composition of crops

The synthesis of vitamins in plants directly depends on the availability of macro- and micronutrients in the soil. The root system of crops does not just supply minerals, but also acts as an organ of biosynthesis for many physiologically active compounds itself. The relationship is simple: some elements are directly included in the structure of vitamin molecules (nitrogen, sulfur, cobalt), while others (phosphorus, potassium, magnesium, calcium, iron) activate the enzyme systems that carry out biosynthesis.

Nitrogen nutrition enhances the formation of vitamins B1, B2, B6, ascorbic acid, and carotene. The application of phosphate and potash fertilizers creates an optimal environment for the active progression of these biosynthetic processes. If plants experience a deficiency of essential nutrients, the accumulation of vitamins slows down sharply.

Micronutrients act as catalysts for the enzyme systems responsible for the formation of vitamins. Foliar top dressing and optimization of the micronutrient composition of the soil allow for the targeted modification of the biochemical profile of the harvest:

• Zinc, manganese, copper, cobalt, and molybdenum enhance the accumulation of ascorbic acid and carotene in tissues.
• Copper is essential for the biosynthesis of vitamin PP (nicotinic acid).
• Manganese activates the formation processes of thiamine (vitamin B1).
• Cobalt is directly involved in the synthesis of vitamin B12.

The application of micro-fertilizers directly accelerates the accumulation of dry matter in the marketable part of the harvest. Copper, zinc, boron, magnesium, iron, and molybdenum interact with vitamins to form highly active complex compounds and enzymes. This synergy activates plant enzyme systems, which accelerates the synthesis of proteins and carbohydrates in the cells.

To initiate these processes, it is important to ensure the availability of elements that are part of enzyme complexes:

• magnesium and iron;
• copper and zinc;
• boron and molybdenum.

The influence of mineral balance on root system development

In the case of nutrient deficiency, the biosynthesis of vitamins in tissues slows down sharply. This triggers a chain reaction: the overall metabolism is disrupted, and root nutrition, in which vitamins are directly involved, is blocked. As a result, plants lose the ability to fully absorb nutrients from the soil solution.