Phosphorus (P) is essential for all living organisms. Plants must have phosphorus for normal growth and maturity. Phosphorus plays a role in photosynthesis, respiration, energy storage and transfer, cell division, cell enlargement and several other processes in plants. A plant must have phosphorus to complete its normal production cycle.
Phosphorus is an essential nutrient both as a part of several key plant structure compounds and as a catalysis in the conversion of numerous key biochemical reactions in plants. Phosphorus is noted especially for its role in capturing and converting the sun's energy into useful plant compounds.
Phosphorus is a vital component of DNA, the genetic "memory unit" of all living things. It is also a component of RNA, the compound that reads the DNA genetic code to build proteins and other compounds essential for plant structure, seed yield and genetic transfer. The structures of both DNA and RNA are linked together by phosphorus bonds.
Phosphorus is a vital component of ATP, the "energy unit" of plants. ATP forms during photosynthesis, has phosphorus in its structure, and processes from the beginning of seedling growth through to the formation of grain and maturity.
Thus, phosphorus is essential for the general health and vigor of all plants. Some specific growth factors that have been associated with phosphorus are:
Stimulated root development
Increased stalk and stem strength
Improved flower formation and seed production
More uniform and earlier crop maturity
Increased nitrogen N-fixing capacity of legumes
Improvements in crop quality
Increased resistance to plant diseases
Supports development throughout entire life cycle
Phosphorus Deficiency in Plants
Phosphorus deficiency is more difficult to diagnose than a deficiency of nitrogen or potassium. Crops usually display no obvious symptoms of phosphorus deficiency other than a general stunting of the plant during early growth. By the time a visual deficiency is recognized, it may be too late to correct in annual crops. Some crops, such as corn, tend to show an abnormal discoloration when phosphorus is deficient. The plants are usually dark bluish-green in color with leaves and stem becoming purplish. The degree of purple is influenced by the genetic makeup of the plant, with some hybrids showing much greater discoloration than others. The purplish color is due to accumulation of sugars that favors the synthesis of anthocyanin (a purplish-colored pigment), which occurs in the leaves of the plant.
Phosphorus is highly mobile in plants, and when deficient, it may be translocated from old plant tissue to young, actively growing areas. Consequently, early vegetative responses to phosphorus are often observed. As a plant matures, phosphorus is translocated into the fruiting areas of the plant, where high-energy requirements are needed for the formation of seeds and fruit. Phosphorus deficiencies late in the growing season affect both seed development and normal crop maturity. The percentage of the total amount of each nutrient taken up is higher for phosphorus late in the growing season than for either nitrogen or potassium.