Drought is a world-spread problem seriously influencing grain production and quality, the loss of which is the total for other natural disasters, with increasing global climate change making the situation more serious. Rice is the staple food for more than 23% of world population, so rice anti-drought physiology study is of importance to rice production and biological breeding for the sake of coping with abiotic and biotic conditions. Much research is involved in this hot topic, but the pace of progress is not so large because of drought resistance being a multiple-gene-control quantitative character. On the other hand, stress adaptive mechanisms are quite different, with stress degree, time course, materials, soil quality status and experimental plots, thus increasing the complexity of the issue in question. Additionally, a little study is related to weedy rice.In order to investigate the effects of drought stress on germination and early seedling growth of weedy rice (Oryza sativa f. spontanea L.) and cultivated rice (Oryza sativa L.), polyethyleneglycol-6000 (PEG-6000) are used to generate -1.33MPa and 0MPa water stress in a laboratory condition (28±3°C). Complete randomized design with three replications is used in the study. After 10 days of germination, shoot length, the longest root length, root fresh weight, root dry weight, shoot fresh weight, shoot dry weight and root numbers are measured; germination percentage, and root to shoot ratio are calculated. Germination index (GI), shoot length stress index (SLSI), root length stress index (RLSI) and dry matter stress index (DMSI) are used to evaluate the response of different genotypes to PEG-induced water stress. Results of ANOVA analysis show that responses of weedy rice accessions and cultivated rice varieties to water stress are significant different, demonstrating the germplasm of weedy rice and cultivated rice are diverse which enables us to screen the germplasm tolerant to drought stress.

It detected the canopy temperature of rice via automated infrared imaging technology in the test under different irrigation condition, and used theCWSItheoretical model to diagnose whether the crop suffered water stress or not. It also analyzed the water stress index theoretical model of crop and other indexes on reflecting the water status of crop, including the relationship between theCWSIand leaf stomatal resistance, theCWSIand leaf net photosynthetic rate, and theCWSIand the soil moisture content. The results showed that the relations between the surface theoretical model and the above indexes were fine. It meant theCWSIwell reflected the features of water stress of rice.

It detected the canopy temperature of rice via automated infrared imaging technology in the test under different irrigation condition, taking the Idso empirical model to determine the lower bound equation of the canopy-air temperature differences, and so to get the best period of observing the rice water deficit by theCWSI, in addition the relationship of theCWSI, soil water content and transpiration rate were also analyzed. The preliminary test analysis showed that theCWSIcan reflect the rice water stress conditions well.