Effects of sunshine-shading, leaf-cutting and spikelet-removing on yield and quality of rice in the high altitude region

中国人. 通过遮光、剪叶和疏花等措施，研究了高海拔地区水稻源库关系对籽粒灌浆及稻米品质的影响，以及灌浆物质和灌浆动态与稻米品质的关系。结果表明，遮光可提高整精米率，特别是对强势粒；遮光对垩白度的影响因品种和粒位而异；剪叶提高垩白度，而疏花降低垩白度；遮光降低稻米直链淀粉含量和稻米淀粉RVA谱的最高黏度和崩解值，延长米胶长度；稻米主要品质指标既与灌浆物质量有关，也与灌浆动态有关。灌浆结实前期的灌浆速率、灌浆量及其比例对垩白面积、垩白度、最高黏度、崩解值等影响最大，后期其次，中期的影响较小；垩白面积和垩白度随结实前期灌浆速率、灌浆量及其比例的增加而降低，随结实后期灌浆速率、灌浆量及其比例的增加而增加，最高黏度、崩解值则相反。

英语. There have been a lot of reports on the relationship between source-sink state and yield, milling quality and appearance quality in rice, but few reports on the relationship between source-sink state and the RVA profile of rice starch, as well as the relationship between rice quality and grain filling process in rice in the high altitude region. With a purpose of revealing the substantial base of quality formation, the effects of source-sink state on rice quality and the relationship between grain-filling process and rice quality were studied in this paper. The experiments were conducted in a high altitude region by sunshine shading, leaf-cutting and spikelet-removing treatments. The results were as follows： The milled rice rate was reduced but the head milled rice rate increased by sunshing shading, especially for superior grains（Table 2）. Under the sunshine shading condition, the chalkiness degree was varied with cuhivars and grain positions. The chalkiness degree was increased by leaf-cutting and reduced by spikelet-removing （Table 3）. The amylose content, the value of peak viscosity and breakdown viscosity of RVA profile of rice starch were reduced, but the length of rice gel was elongated by sunshine shading in the two experimental cuhivars（Table 4）. The source-sink state showed a big effect on the grain filling process （Table 5）. The area and the degree of chalkiness were negatively correlated with the final grain weight and positively correlated with the days to maximum grain filling rate. The peak and breakdown viscosity of rice starch were positively correlated with the final grain weight and negatively correlated with the days to maximum grain filling rate （ Fig. 1 ）. The grain-filling rate, the amount of dry-matter filled and its ratio to total weight during the early filling stage（ 15 days after full heading） had the most effect on rice quality, less effect during the late filling stage（30 days after full heading） and the least effect during the middle filling stage（ 15 - 30 days after full heading）. During the early filling stage, the grain-filling rate, amount of dry matter filled and its ratio to total weight increased, the area and degree of chalkiness decreased and the peak and breakdown viscosity of rice starch increased. While during the late filling stage, the grain-filling rate, amount of dry matter filled and its ratio to total weight were increased, the area and degree of chalkiness increased and the peak and breakdown viscosity of rice starch decreased （table 6）. The rice quality is influenced not only by the total amount of grain- filling matter, but also by the grain-filling process. The effect of sunshine shading on rice qulaity in the high altitude region is not fully similar to that in low altitude region.