Almost all elements of the periodic system of D.I. Mendeleev, but the role of many of them is still insufficiently understood.
Plants absorb nitrogen, phosphorus, potassium, calcium, magnesium, sulfur in the greatest quantity. These elements are called macronutrients, their content in plants is calculated in whole percentages or tenths.
Nitrogen (N) is a part of all proteins, nucleic acids, amino acids, chlorophyll, enzymes, many vitamins, lipoids, and other organic compounds formed in plants. Lack of nitrogen causes the cessation of growth and yellowing of the leaves due to the violation of chlorophyll formation.
Nitrogen is a very mobile element; if it is deficient, it moves from old leaves to new, younger ones. Signs of nitrogen starvation appear - first in the yellowing of the lowest leaves, and then, if the process is not stopped, in the death of the leaves above.
An excess of nitrogen leads to unnaturally rapid growth, the formation of loose tissues, which makes them more susceptible to various diseases. The growing season is lengthened and the beginning of flowering is delayed; in some plants, an overdose of nitrogen fertilizers can shift internal processes so much that it will lead to a complete rejection of flowering. Excess nitrogen also delays the absorption of potassium by the plant.
Phosphorus (P) plays an extremely important role in plant life. Most metabolic processes are carried out only with his participation. It ensures the health of roots, the laying of buds, the ripening of fruits and seeds, and increases winter hardiness.
With a lack of phosphorus, flowering and ripening are delayed, defective fruits are formed, the leaves acquire a red-brown tint. First of all, the old lower leaves are affected, then the process spreads higher.
Excess phosphorus slows down the metabolism, makes the plant less resistant to lack of water, impairs the absorption of iron, potassium and zinc, which leads to general yellowing, chlorosis, the appearance of bright necrotic spots, and leaf fall. The development of the plant is accelerating, it ages quickly.
Some plants react particularly negatively to high doses of phosphorus fertilizers. This applies, first of all, to people from Australia, where the soils are poor in phosphorus. Coniferous plants do not like feeding with phosphorus. Hibiscuses also require special care when introducing this element, for which it is not recommended to use fertilizers rich in phosphorus for flowering plants.
Potassium (K) plays an important physiological role in carbohydrate and protein metabolism in plants, in the processes of photosynthesis and water metabolism, increases resistance to wilting and premature dehydration, strengthens plant tissues and makes them more resistant to diseases and pests.
It easily moves from old plant tissues, where it has already been used, to young ones. The lack of potassium, as well as its excess, negatively affects the quantity and quality of the crop. With an excess of potassium, the flow of nitrogen into the plant is delayed, growth inhibition, deformation and chlorosis of leaves, primarily old ones, occurs. In later stages, mosaic spots appear, the leaves wither and fall off. Excess potassium also impairs the absorption of magnesium or calcium.
Magnesium (Mg) is part of chlorophyll and is directly involved in photosynthesis. And it is also necessary for the formation of a reserve substance of phytin, contained in plant seeds, and pectin substances.
Magnesium activates the activity of many enzymes involved in the formation and transformation of carbohydrates, proteins, organic acids, fats; affects the movement and conversion of phosphorus compounds, fruiting and seed quality. The maximum content of magnesium in the vegetative organs of plants is observed during the flowering period. After flowering, the amount of chlorophyll in the plant sharply decreases and magnesium flows out of the leaves and stems into the seeds, where phytin and magnesium phosphate are formed.
Lack of magnesium manifests itself in yellowing of leaves, chlorosis.
Calcium (Ca) is involved in carbohydrate and protein metabolism of plants, the formation and growth of chloroplasts. It is necessary for the normal assimilation of ammonia nitrogen by the plant, and makes it difficult to restore nitrates to ammonia in plants. The construction of normal cell membranes is highly dependent on calcium.
Unlike nitrogen, phosphorus and potassium, which are usually found in young tissues, calcium is found in significant quantities in old tissues; moreover, it is more in leaves and stems than in seeds.
Sulfur (S) is a constituent of the amino acids cystine and methionine, is an integral part of proteins and some vitamins, and influences the formation of chlorophyll. Lack of sulfur leads to chlorosis, primarily of young leaves.
Phalaenopsis hybrid Anthura Leeds
Other nutrients are no less important - iron, copper, manganese, molybdenum, zinc, cobalt, boron, etc., which are commonly called trace elements. They are consumed by plants in small quantities, but lack of them leads to serious defects in plant development. The content of trace elements in a plant is calculated in hundredths and thousandths of a percent.
Iron (Fe) is part of the enzymes involved in the construction of chlorophyll, although this element is not directly included in it. Iron is involved in redox processes in plants; it is an integral part of respiratory enzymes. Lack of iron leads to the breakdown of growth substances (auxins) synthesized by plants, while the leaves become pale yellow. It is most often observed with an excess of carbonates and in heavily limy substrates. Iron cannot move from old tissues to young ones.
- Copper (Cu) is a part of copper-containing proteins, enzymes, it also takes part in the process of photosynthesis, carbohydrate and protein metabolism.
- Manganese (Mn) is a part of redox enzymes and takes part in photosynthesis, carbohydrate and nitrogen metabolism.
- Molybdenum (Mo) plays an important role in nitrogen nutrition. It is localized in young growing organs and less in stems and roots. With a lack of molybdenum, the development of nodules on the roots of leguminous plants and nitrogen fixation are delayed. The introduction of molybdenum into the soil facilitates the absorption of nitrogen fertilizers by plants, but a high content of molybdenum is very toxic to plants.
- Zinc (Zn) influences the metabolism of energy and substances in the plant. With a lack of zinc, the content of sucrose and starch decreases, the accumulation of organic acids increases, the content of auxin decreases, protein synthesis is disrupted, and growth retardation is characteristic.
- Cobalt (Co) is involved in the biological fixation of molecular nitrogen.
- Boron (B) is involved in the reactions of carbohydrate, protein, nucleic acid metabolism and other processes. Plants need it throughout their life. Young leaves and growth points primarily suffer from its deficiency. Excess boron burns the lower leaves, they turn yellow and fall off.
The deficiency of a certain nutrient will not slow down the effect on the development of the plant, but it is often very difficult to determine the true cause of the impaired growth. An excess of one element can inhibit the absorption of another, therefore, introducing an excess of one substance, we can cause starvation in another. It is important not only to add all the necessary nutrients, but also to choose the right ratio.
Continued in the article Feeding indoor plants.
Photo: Rita Brilliantova