Changes in nitrogenous fractions of certain crop plants as affected by phosphorus deficiency

Abstract

Plants of Phaseolus radiatus variety T. I, Vigna catjang variety Early Buff, Cicer arietinum variety T.87, and Linum usitatissimum variety NP(RR)5 grown in sand were supplied with complete or phosphorus-deficient nutrient solution. The deficiency symptoms were, in general, stunted plant growth, dark green leaves and marked reduction in leaf area. Leaves, stems and roots of deficient and control plants were analyzed for total, soluble and protein nitrogen and for amounts of different amino acids. Total and soluble nitrogen increased while protein nitrogen decreased in all three parts of phosphorus-deficient plants as compared to controls. Moreover, there was an increase in soluble nitrogen as a percentage of total nitrogen; this suggested that the heavy accumulation of total nitrogen resulted mainly from the increase in soluble nitrogen. Chromatographic assay of the root, stem, and leaf revealed that soluble amino acids and amides accumulated in considerably higher amounts in the phosphorusdeficient plants as compared to controls. The degree of accumulation of individual amino acids and amides in phosphorus-deficient plants varies not only from species to species but also from organ to organ of the same plant. An accumulation of arginine was common feature of phosphorus deficient plants of all four species.