Post-anthesis Water Stress and Nitrogen Rate Effects on Dry Matter and Nitrogen Remobilisation in Wheat Cultivars

摘要

Grain yield and protein in wheat are determined by the plant efficiences in partitioning dry matter and Nitrogen (N) to the grain. The interaction between post-anthesis water stress and nitrogen rate was examined in six wheat cultivars. Plant were grown in a glasshouse at 2 rates of N under well-watered conditions until 7 days affer ear emergence, when the stress treatment was started. Yield and Grain Protein Concentration (GPC) responses and changes in the dry matter and N content of the straw and grain in the main stem and tillers were examined. Nitrogen increased grain yield in all cultivars except Fong, with Atila and Falat being the most responsive. Yields at the low N rate did not reduce by post-anthesis stress, but large reductions occurred at the high N rate in all cultivars; the yield of Falat, Showa and Atila were most affected. At the low N rate, stress did not significantly affect kernel weight and GPC, but kernel weight declined and GPC increased at the high N rate. Tillers produced smaller grain with a lower GPC than main stem. The responses to N and water stress and the different sensitivities of cultivars to stress, were largely due to the effects of the treatments on the growth of the tillers. Net remobilisation of dry matter was increased by stress but not by N treatment and the amount remobilised varied between genotypes. Post-anthesis stress increased the N content per kernel and net remobilisation of N at the high N rate. Although genotypes differed in the net amount of N remobilised and in the N harvest index, there was little variation in GPC between cultivars. Results showed that reductions in yield and kernel weight and increases in GPC from post-anthesis stress can be greater when plants are grown at a high rate of N than when the supply of N is limited. The different responses to stress and N among the six wheat cultivars were associated, in part, with the pattern of tiller development. However, there appeared to be differences in the sensitivity of grain filling to stress independent of the responses in tillering. While the net remobilisation of dry matter and N differed between cultivars, the amounts did not appear to be related to differences in GPC.