Effect Of Low-light Stress On Rice Grain Growth And Grain Quality After Heading

A three-replicate, split-plot design was used with species as main plot treatments and shading as the subplot treatments. Species treatments included Indica hybrid II you 162 , Dyou68 and Gangyou22. Shading treatments began after 10% panicles heading, and subplot treatments were wrapped with one or two layers of 49%-shade or 69%-shade. The characteristics of leaves, plant dry weight, grain weight and grain quality were measured. The main results were as follows. 1, These characteristics of leaves were obviously affected by the low-light stress. Firstly, the length and the width under low-light stress were higher than the control. Secondly, the average LAI of each species in 49%-shade was higher than control, and the LAI of each species in 69%-shade was lower than that in 49%-shade. Thirdly, the SLA of Dyou68 and Gangyou22 increased, but that of II youl62 decreased while the light-density decreased. Finally, the chla, chlb, chl(a+b) increased, and chlalb decreased while light-density decreased. 2, Shading reduced plant dry weight, and the distribution and transformation of dry matter was obviously affected by shading. Shading decreased the dry matter production and accumulation rate, and the export and transformation percentage of the dry matter in steams and sheaths were increased by shading. At the same time, the distribution of dry matter to panicles and NAR reduced relative to control. 41 3, Low-light stress seriously limited the rice grain growth. As light density reduced and the time of low-light stress lengthened, the empty grain rate increased continuously. The highest grain weight, grain filling rate and the relative initial grain filling power decreased under the low-light stress, and the grains-filling parameters of whole grains were less than that of superior grains. At the same time, the contribution of early, middle and late stage of grain filling to the final dry weight also changed in different light density. 4, Grain yield of rice was significantly affected by shading, because low-light stress affected the seed-setting rate, grain-weight and grain filling. The seed-setting rate was reduced 27.8% by 49%-shade and 44.2% by 69%-shade. 5, The synthetic rice grain quality was significantly reduced by low-light stress. As light density decreased, the 10 single (except Amylase content and protein) qualities were significantly worse than controls, especially, the chalk kernel rate and the chalk degree were significantly higher than the unstressed. But the AC (amylase content) and protein got better by shading. AC significantly decreased and protein significantly increased while light density diminished. The main cause that rice grains quality was reduced by low-light stress was that the grains growth became worse in shading, and low-light stress affected the exterior kernel quality, moreover, the market quality and the eating quality became worse. Finally, the cause that protein increased under low-light stress and the approaches to regulate rice grains quality and yield were discussed.