(1) nitrogen is the main component in protein, and the average nitrogen content in protein is 16% ~ 18%. All living things are in the process of continuous synthesis and decomposition in protein. Once this metabolism stops, life will also end. Nitrogen is an important component of nucleic acid, which is the basic substance of plant growth, development and life activities. It exists in a large number of nuclei and meristems at the top of plants and is an important substance carrying genetic characteristics. Nitrogen is a constituent element called green pigment. Plants use and absorb solar energy through chlorophyll to carry out photosynthesis and produce organic matter. Nitrogen is a component of many enzymes in plants. Enzymes can catalyze various metabolic processes in plants, and enzyme systems control the direction and speed of many chemical reactions. Nitrogen is also a component of some vitamins and alkaloids, such as vitamin B 1, B2, B6, nicotine and theophylline. Without nitrogen, these substances cannot be formed.
(2) Phosphorus is a component of many important organic compounds in plants. Although some compounds do not contain phosphorus, phosphorus must also participate in their formation and transformation. Phosphorus is a component of plant nucleus, and phosphorus is also the main component of nucleic acid. These substances are extremely important to the growth, development and metabolism of plants, and nucleic acid is a substance carrying genetic characteristics. Phosphorus can promote plant root development, robust growth and the formation of new organs. Phosphorus is also an important component of phospholipids. There are many kinds of phospholipid compounds in plants. Phospholipids can also form biofilms on the inner and outer surfaces of protoplasm together with membrane lipids such as glycolipids, and become the gateway to ensure and regulate the entry and exit of substances into cells. It is selective for the entry and exit of substances and can regulate life activities. Phosphorus also participates in the metabolism of carbohydrates, nitrogen compounds and fats in plants, and in these processes, phosphorus is also transformed into various phosphorus-containing organic compounds, so phosphorus has obvious effects on dry matter accumulation, starch synthesis, sugar and oil content of plants. Because phosphorus promotes various metabolic processes in crops, it can relatively advance the growth period of crops, which is conducive to promoting early maturity. Phosphorus can also improve the resistance and adaptability of crops to external environmental conditions, and can improve the drought resistance and cold resistance of crops. Phosphorus plays an important role in plant growth and development.
(3) Sulfur is one of the important constituent elements of protein, and it is also the structural component of many coenzymes and auxiliary groups. Sulfur-containing organic compounds in crops also participate in the redox process, and sulfur has a special effect on crop respiration. Sulfur deficiency hinders the formation of protein, rather than the accumulation of protein nitrogen, thus affecting the content of protein in the body and ultimately affecting the yield of crops. Sulfur deficiency will also reduce chlorophyll content, turn leaves from pale to light green, shorten leaf life and reduce photosynthesis. Sulfur can promote the formation of root nodules in leguminous crops. Sulfur is also one of the important components of sulfur-containing compounds with volatile and special odor, such as cruciferous onion, garlic and mustard oil.