关键词: 前期遮光, 水稻, 剑叶, 生理特性, 籽粒生长, 籽粒产量, 外源硅, 花期高温, 杂交水稻, 授粉结实

Abstract: In a pot experiment, rice plants were shaded during the period from tr
ansplanting to booting, aimed to study the effects of early growth stage shading
 on the rice growth at grain-filling stage. Comparing with the control, early g
rowth stage shading decreased the tiller number by 2672%, but increased the fl
ag leaf area and soluble sugar content by 3386% and 3023%, respectively. The
 filled-grain number per panicle, 1000-grain mass, ultimate brown rice mass,
  and maximum and average grain-filling rates decreased by 865%, 481%, 97
4%, 2022%, and 1913%, and the effective panicle number and grain yield decli
ned by 2526% and 3956%, respectively. The peak time of grain-filling rate (Tm) advanced 166 days, while the grain-filling time  (T99) prolonged 680 da
ys. For shading-tolerance variety, its flag leaf Chl a, Chl b, and Chl (a+b) co
ntents at early and mid grain-filling stages, and the protein N and soluble su
gar contents and Chl a/b in its flag leaves at grain-filling stage all increase
d under early growth stage shading, and the ultimate brown rice mass and 1000-g
rain mass maintained at the similar levels as the control. Consequently, its grain yield reduction rate was lower than that of shading-sensitive variety.

Key words: early growth stage shading, rice, flag leaf, physiological characters, grain growth, grain yield, exogenous silicon, heat stress during anthesis, hybrid rice, pollination and fertility.