Effect of Light Deficiency During Different Growth Stages on Grain Yield and Quality of Super-hybrid Rice,II Youhang 2

To understand the effect of deficient sunlight on the super rice production in light-poor areas,a field experiment was conducted.The super-hybrid rice,Ⅱ Youhang 2,was used for the study.At the early(transplanting),middle(jointing) and late(initial heading) stages,rice grain yield and quality were determined with 55% shading for 14 days,in comparison to those under the natural light condition as the control.The results showed that the shading at the transplanting stage significantly decreased the filler number and the leaf area index.It also reduced the effective panicle number by 10.77%,and the yield by 6.70%.The yield loss was due to insufficient supply of nutrients.But,there was no significant difference in the grains quality.At the jointing stage,the shading caused significant inhibition of stem growth and sheath dry matter accumulation.It decreased the grains per panicle by 14.26%,1000-grain weight by 7.87%,and the yield by 22.44%.The yield reduction was attributed to the decreased sink.Meanwhile,the processing quality,such as the unrefined rice rate,the milled rice rate and the head milled rate,was decreased as well.At the initial heading stage,the shading decreased the percentage of filled grains,as well as,the grain-set rate and 1000-grain weight by 26.54% and 14.10%,respectively.The yield became the lowest among all treatments,i.e.,a reduction of 36.14%.Poor in nutrient flow was thought to be the main reason leading to the yield reduction.The grain quality of the rice shaded at initial heading stage was significantly inferior to that of the control.Thus,it was concluded that the greatest effect of deficiency in sunlight exposure on the super-hybrid rice occurred in the initial heading and grain filling stages,followed by the young spike development and the vegetative growth stages.