H. Usuda, PHOSPHATE DEFICIENCY IN MAIZE .5. MOBILIZATION OF NITROGEN AND PHOSPHORUS WITHIN SHOOTS OF YOUNG PLANTS AND ITS RELATIONSHIP TO SENESCENCE, Plant and Cell Physiology, 36(6), 1995, pp. 1041-1049
The effects of phosphorus (P) deprivation on the changes in the conten
ts 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, tot
al P, esterified P, acid-soluble P-i, total reduced N, soluble protein
N, and insoluble protein N in the entire shoot. Thirty DAP, in the fi
fth leaf blade, which was expanding, P deprivation greatly decreased t
he concentration of acid-soluble P-i but had a smaller effect on the c
oncentration of esterified P and little or no effect on the concentrat
ions of Chi, total reduced N, soluble protein N, and insoluble protein
N. By contrast, in the fully expanded second leaf blade, P deprivatio
n greatly decreased the contents of acid-soluble P-i, esterified P, Ch
i, total reduced N, soluble protein N, and insoluble protein N at 30 D
AP. It is concluded that P deprivation induced the early initiation an
d accelerated remobilization of N from old leaf blades. Since this phe
nomenon is a critical feature of leaf senescence, it is suggested that
the P status of leaves is involved in the regulation of leaf senescen
ce in maize.