| The experiments were carried out at Lingshui, Hainan and Baihe, Shanghai respectively. All varieties used in this study were provided by Shanghai agrobiological gene center. Materials were classified into 5 grades:1,3,5,7 and 9-grade which means highly resistant, resistant, moderately resistant, moderately sensitive and sensitive to drought respectively. Drought stress was implemented by natural drought stress in Hainan and water gradient stress technique in Shanghai. The physiological and biochemical changes between materials and drought and water control treatment were measured. The relationship among physiological traits, yield and yield related traits under water and drought conditions were analysed. The results are as follows:1. The amount of grain yield decresed in 1-grade materials is smaller than that in other 4 categories. And 1 grade materials hold higher DR index (DI). Correlation analysis indicated that grain yield was extremely significant positive correlated with PN, BIM, GNP, SF, HGW, and DC in 1-grade materials population. While, it was significant positive correlated with PL, GNP, SF, HGW, DI and BIM in 9-grade materials population in Shanghai.2. The leaf water content reduced with the intensification of drought stress. The amount of leaf water content decreased in 1-grade materials was less than that in 9-grade materials. Accoding to the ANOVA results, the change of leaf water content under drough and water condition in 5 drought resistant categories was significantly different. Furthere more, it is also significantly different between varieties in 9-grade population. While there were no significant differences between the varieties in 1,3,5 and 7-grade population.3. Chlorophyll content decreased with the intensification of drought stress. In 1-grade population, the change of the ratio of chlorophyll a and chlorophyll b under drought and water conditon is less than that in 9-grade population. Correlation analysis indicated that chlorophyll a and chlorophyll b had close relationship with drought resistance. The ratio of the content of chlorophyll a and chlorophyll b was significant or extremely significant negtive correlated with DI in 1-grade population, while there was no significant correlation in 9-grade population.4. The content of proline (Pro) and soluble sugar (Ss) increased with the deepening of drought stress, while the change of soluble protein (Sp) was on the contrary. Correlation analysis indicated that Ss was opositive correlated with SOD and POD in 1-grade population but positive correlated with SOD and POD in 9-grade population. There was opositive correlation between Ss and DI in 1-grade population, while in 9-grade population, negtive correlation was found between Ss and DI. The content of Pro had significant positive correlation with grain yield both in 1-grade and 9-grade population. 5. The content of MDA increased with the development of drought stress. The increased amount of content of MDA in 1-grade population is less than that in the 9-grade population. The activitiy of SOD and POD creased with intensification of drought degree. Correlation analysis indicated that there was high significant correlation between SOD activity and POD activity in 1-grade populatin, but positive correlation in 9-grade population. POD activity was extremly significant positive correlated with DI in 1-grade materials, while it was not significant correlated with DI in 9-grade materials.
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