| Abstrakt: |
A field experiment was conducted with high and low N fertility regimes to evaluate root-absorbed 15N, and its subsequent remobilisation in four maize hybrids. In previous experiments, potential yield and patterns of senescence had varied among these hybrids. Individual plants were supplied with 15N at the 12-leaf stage and the uptake of the labelled N and its subsequent partitioning during successive harvests was followed. Grain yield and N accumulation at physiological maturity (PM) were reduced 20 and 40%, respectively, under low N compared with high N fertility. Neither hybrid type nor N fertility level initially affected the amount of lSN absorbed. Maximum 15N content was observed at mid grain-fill and a significant 10% loss of 15N from plants was found at PM. Compared with those under low N, plants cultured under high N maintained higher percentages of 15N in the lower stalk and roots over hybrids and across harvests. Kernels were a sink for remobilised 15N from all vegetative and 'other' reproductive tissues. Patterns of N remobilisation varied among different vegetative tissues. N was remobilised from stalks earlier than from leaves, while N from roots was remobilised throughout the season. Stalk and leaves were the major sources of 15N for kernels (about 45% each) while roots contributed much less. Physiological differences between the hybrid with the highest yield at both fertility levels, and with other hybrids, are discussed. |
