Phosphate deficiency in maize. V. Mobilization of nitrogen and phosphorus within shoots of young plants and its relationship to senescence. Plant Cell Physiol

The effects of phosphorus (P) deprivation on the changes in the contents of reduced nitrogen (N) and P in the shoots of young maize plants (Zea mays L.) were investigated for up to 30 days after planting (DAP). P deprivation decreased the fresh weight and the contents of Chi, total P, esterified P, acid-soluble P|, total reduced N, soluble protein N, and insoluble protein N in the en-tire shoot. Thirty DAP, in the fifth leaf blade, which was expanding, P deprivation greatly de-creased the concentration of acid-soluble P | but had a smaller effect on the concentration of esterified P and little or no effect on the concentrations of Chi, total reduced N, soluble protein N, and insoluble protein N. By contrast, in the fully expanded second leaf blade, P deprivation great-ly decreased the contents of acid-soluble P,, esterified P, Chi, total reduced N, soluble protein N, and insoluble protein N at 30 DAP. It is concluded that P deprivation induced the early initiation and accelerated remobilization of N from old leaf blades. Since this phenomenon is a critical feature of leaf senescence, it is suggested that the P status of leaves is involved in the regulation of leaf senescence in maize. Key words: N mobilization — Phosphorus deficiency — Senescence — Zea mays. The availability of phosphorus (P) is one of the mos