Dry matter and nitrogen accumulation in grains at different ear positions in ‘gigas’, semidwarf and normal spring wheats

Summary

Distribution and accumulation of dry matter (d.m.) and nitrogen (N) were investigated within ears of a semidwarf, a gigas, and a normal wheat genotype grown under controlled environments. A high harvest index was linked with a small pre-anthesis N-storage (and vice versa) but this did not affect N amounts in grains because of compensation by prolonged N uptake during grain filling. N distribution within and between spikelets roughly paralleled that of d.m. Nevertheless, the two processes appeared to be rather independent as became evident from comparisons of the time courses in and between the genotypes. Final distribution of d.m. and N within and between spikelets mainly depended on different rates during the linear phases of accumulation and less on the duration. Maximum of d.m. and N weights per grain as well as maximum of grain number were observed in spikelets below the middle of the ear axis. This ‘submedian dominance’ suggested a pre-anthesis determination of the accumulation potential of grains in different spikelets. N percentage within spikelets disclosed that N accumulation was hampered more than that of d.m. in those positions unfavourable to the latter process. This principal pattern was not affected by genotypes in spite of considerable differences in numbers and weights of grains.