Essential Role Of Phosphorus (P) In Plants
Phosphorus is an essential nutrient both as a part of several key plant
structure compounds and as a catalyst 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. The two examples that follow illustrate how vital phosphorus
nutrition is to normal plant development and production. 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 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, and 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, some hybrids showing much greater discoloration than others. The purplish color is due to accumulation of sugars which favors the synthesis of anthocyanin (a purplish colored pigment) that 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.
Soil Phosphorus Availability