Seed Setting Characteristics And Response To Weak Light Stress Of Rice Varieties With High Efficiency

The new development requirement of rice production in China has changed from high yield to high efficiency and high yield.With the improvement of science and technology,the popularization and application of the modern cultivation mode of machine transplanting rice not only brings convenience,but also leads to the problem of shorter growth period.Therefore,modern rice varieties need to make adaptive changes to achieve high yield through efficient matter production in a shorter growth period.However,the current research on the efficiency of rice mainly focuses on the efficiency of nitrogen resource absorption and utilization,while the research on the efficiency of matter production is less.This study with five different types of hybrid rice and conventional japonica rice used as test materials,by the way of simulating machine transplanting,from matter production,grain filling,nitrogen use and yield formation,etc,analyzed the type characteristics of high efficiency and high yield varieties,and by setting different levels of nitrogen treatment and weak light stress,respectively,to explore high efficiency and high yield varieties of nitrogen response differences as well as the resistance research of weak light.The research results can provide the necessary theoretical basis and experimental support for the formation of high efficiency and high yield technology system and the selection of modern adaptive varieties under the cultivation mode of machine transplanting rice.The main results are as follows:1.According to the daily production rate and yield,varieties were divided into three types:high efficiency and high yield,low efficiency and high yield,and general varieties High efficiency and high yield varieties had higher population storage capacity and higher seed setting rate and spikelets per panicle of hybrid rice and the effective panicles of conventional japonica rice were the key factors for the formation of high population storage capacity.High efficiency and high yield varieties had higher net photosynthetic rate during grain filling stage.Lower stem sheath transference and transfer rate,and lower contribution of stem and leaf dry matter transfer to panicle,indicating that matter accumulation in panicle of high efficiency and high yield varieties was more dependent on photosynthetic product accumulation,while the utilization of the storage materials in stem sheath was less dependent.In addition,the high stem sheath dry matter in late grain filling stage of high efficiency and high yield varieties delayed the senescence of stem sheath to some extent,and maintained the strong physiological function of stem sheath.2.Compared with general varieties,the high efficiency and high yield varieties had higher nitrogen concentration in the stem and leaves at the heading stage,and higher nitrogen concentration in the panicles at mature stage.The nitrogen transport capacity of vegetative organs to the panicles from heading stage to mature stage was strong.The activities of nitrate reductase(NR),glutamine synthetase(GS)and glutamate synthase(GOGAT)in the leaves of high efficiency and high yield varieties were significantly higher than those of general varieties,and the ability of nitrogen assimilation was stronger.3.Compared with general varieties,the flag leaf net photosynthetic rate and daily matter production rate decreased slightly when high efficiency and high yield varieties encountered different degrees of weak light at the filling stage and the yield decreased slightly at the same time.The results showed that high efficiency and high yield varieties had better resistance to weak light stress,which was mainly reflected in higher daily matter production capacity compensating for the decrease of light contract capacity caused by weak light stress to some extent.After 30%shading for 20 days,normal light was restored,and the daily matter production rate and yield of the tested varieties recovered to different degrees,while high efficiency and high yield varieties showed better recovery ability.4.The superior spikelets of high efficiency and high yield varieties had the characteristics of large initial growth potential,great seed growth potential,short active filling period,fast filling rate and reaching the maximum filling rate earlier,indicating that the high efficiency and high yield varieties can finish superior spikelets filling quickly in a relatively short time.However,compared with high efficiency and high yield varieties,the initial growth potential of inferior spikelets was relatively low,and the filling time was long and the filling rate was small.The accumulation of grain filling substances was slow,and the difference between the final grain weight of superior spikelets and inferior spikelets was large,which was an important reason for the low seed setting rate of the general varieties The activities of sucrose synthase(SS)and ADP-glucose pyrophosphorylase(ADPG),the key enzymes in grain development,were higher in the high efficiency and high yield varieties than in the general varieties during grain filling period.Under different degrees of weak light stress,the inferior spikelets were significantly affected,grain plumpness became worse,and the final grain weight decreased to different degrees.Compared with the general varieties,the high efficiency and high yield varieties had a smaller decrease in inferior spikelets and a higher seed setting rate,which was the key for high efficiency and high yield varieties to achieve a relatively high yield under weak light stress.5.There was no significant difference in the processing and appearance quality,eating quality and RVA profile characteristics between high efficiency and high yield varieties,low efficiency and high yield varieties and general varieties.The comprehensive characters of rice were different among the same variety type.However,the comprehensive characters of rice quality were significantly different at different nitrogen fertilizer levels,and too much or too little nitrogen fertilizer-application resulted in poor quality.Under weak light stress,the chalkiness and setback values of rice increased,amylose content,gum consistency and breakdown values decreased.The degree of rice quality deterioration under weak light stress had no obvious correlation with the variety type.The comprehensive characters of rice were improved after the light was restored in the middle and late grain filling stage.