Effect of delayed sowing on grain number, grain weight, and protein concentration of wheat grains at specific positions within spikes
Jinpeng Chu, Xin-hu GUO, Feina Zheng, Xiu ZHANG, Xinglong Dai, Mingrong He
Abstract
Delays in sowing have significant effects on grain yield, yield components, and grain protein concentrations of winter wheat. However, little is known about how delayed sowing affects these characteristics at different positions in wheat spikes. In this study, the effects of sowing date were investigated in a winter wheat cultivar, Shannong 30, which was sown in 2019 and 2020 on October 8 (normal sowing) and October 22 (late sowing) under field conditions. Delayed sowing increased the partitioning of 13C-assimilates to spikes, particularly to florets at the apical section of a spike and those occupying distal positions on the same spikelet. Consequently, the increase in grain number was greatest for apical sections, followed by the basal and central sections. No significant differences were observed in superior grain number in the basal and central sections between sowing dates, while the number in apical sections was significantly different. The number of inferior grains in each section also substantially increased in response to delayed sowing. Average grain weight in all sections remained unchanged under delayed sowing because there was a parallel increase in grain number and 13C-assimilate partitioning to grains at specific positions in the spikes. Increases in grain number m-2 resulted in reduced grain protein concentration as the limited nitrogen supply was diluted into more grains. Delayed sowing caused the greatest decrease in grain protein concentration in basal sections, followed by the central and apical sections. No significant differences in the reduction in grain protein concentration were observed between inferior and superior grains under delayed sowing. In conclusion, a 2-week delay in sowing improved grain yield through increased grain number per spike, which originated principally from increased grain number in the apical sections of spikes and in distal positions on the same spikelet. However, grain protein concentrations decreased in each section because of increased grain number and reduced N uptake.