Study On Response To Water Stress And Its Mechanism Of Super Rice (Oryza Sativa L.) Varieties During Flowering-Filling Period In Water Stress

In this study,96of main rice varieties in China were used for drought resistant evaluation. Theseed-setting characteristics and the response of eco-physiological and quality characters were analyzedfor the super rice under water stress. The main results showed as the following:1. The relations between different cultivars and yield components were analyzed with96of thelarge-area application cultivars in China as materials under10d water stress since flowering of maincalm. The results showed that there was no significant difference in the grain number per paniclebetween water stress and CK but both the seed-setting rate and the1000-grain weight were reducedunder water stress compared with CK. According to the water stress index (WSI), the96of the cultivarscould be divided into drought resistant style （WSI＜0.0599）, mid-tolerance style（0.0600＜WSI＜0.2599）and drought sensitive style （WSI＞0.2600）. Through the WSI,9of the cultivars were classedas drought resistant varieties,1of the conventional japonica rice,1of the conventional indica rice,2ofthe two-line indica hybrid rice and5of the three-line indica hybrid rice. The drought resistant of indicarice better than japonica rice and with the same female parent Gang46A, Gangyou527, Gangyou188and Gangyou725showed higher drought resistant in this experiment.2.40super rice varieties were studied on the seed-setting rate,1000-grain weight and grain numberper panicle of superior and inferior grains at flowering stage under water stress. The results showed thatat flowering stage water stress affected the seed-setting rate and1000-grain weight of inferior grainsmost, then the superior grains and grain number per panicle of superior and inferior grains no significanteffects. The effects of water stress on conventional rice seed-setting rate was more significant thanhybrid rice, the seed-setting rate of superior grains less than inferior and water stress affected theseed-setting rate of hybrid rice most.3. Ⅱy ou162and Zhunliangyou527were analyzed for the grain filling at flowering stage indifferent time under water stress. The results showed that the decline of growth capacity of a kernel ofⅡy ou162was more than Zhunliangyou527under the same water stress, and with the time of waterstress prolong, the more decline of growth capacity of a kernel was found. The early-filling stage rate ofgrain filling increased and it took a shortened time to reach the maximum grain-filling rate of grains, themaximum grain-filling rate was decreased and active filling period was increased for inferior grains butsuperior grains were opposite under water stress forⅡ y ou162. The maximum grain-filling rate wasincreased and it took a shortened time to reach the maximum grain-filling rate of inferior grains forFL0-15but the FL0-30was opposite and the same as FL0-30with superior grains and superior andinferior grains active filling period both increased under water stress for Zhunliangyou527.4.4super rice varieties of Zhunliangyou527, Ganxin688, Ⅱy ou162and Yuxiangyouzhanwerestudied on yield characteristics, Physiological and ecological and quality at flowering stage under waterstress. The results showed that because of the seed-setting rate and1000-grain weight decrease led to the yield significant decline ultimately under water stress, the Plant height, leaf area and chlorophyllcontent decreased but stomatal resistance increased at the same time. The water stress influenced thehead rice rate most, then the milled rice rate, the brown rice rate least. Besides part of some varieties ofchalkiness rate and chalkiness decreased, the content of protein increased and amylase decreased underthe water stress.