| Drought stress is an important type of abiotic stress.15%PEG-6000(polyethylene glycol6000) was applied in this study. Results showed that it had no significant effect on the final germination rate of the test weedy rice and cultivated rice, but germination indexex of the weedy rice and cultivated rice were significantly reduced, while germination time of weedy rice and cultivated rice germination time were prolonged. Drought stress significantly reduced the growth rates of weedy rice and cultivated rice, but the reduction of the growth rates of weedy rice was comparatively less than cultivated rice. This suggested that under control treatments, weedy rice and cultivated rice had almost the same growth amounts in terms of ground and underground parts. However, this experiment showed of a trend that under drought stress, growth indexes of weedy rice was greater than that of the cultivated rice. Meanwhile, the weedy rice exhibited an much larger variation range in root length stress index, stem length stress index, the number of stress index, root dry weight stress index, stem heavy stress index than the cultivated rice. Under drought stress, weedy rice root to shoot ratio tends to increase while the cultivated rice root to shoot ratio tends were decrdasing, indicating drought stress had more significantly effect on the root inhibition of weedy rice than on that of the cultivated rice.Repeated drought stress was adopted during seedling stage and drought tolerance was determined. Results showed that the survival rates of weedy rice and of cultivated rice were influenced slightly by the first drought stress, while they were influenced significantly by the second drought stress. In the second drought stress, weedy rice had much larger variation range than the cultivated rice survival rates. During the repeated drought stress experiment, weedy rice LYG07-10had the highest survival rate and weedy rice. HEB07-2had the highest anti-degree range. Drought level was divided according to drought resistance coefficient. The amounts of weedy rice drought resistance of1,3,5,7were8,25,15,6, respectively, making up of the test weedy rice materials12.7%,39.7%,23.8%,9.5%, respectively, which belonged to the normal distribution. That was the weedy rice with the strongest and the weakest drought tolerance was relatively less.During drought stress, leaves and roots mda content and superoxide anion radical production rate of test weedy rice and cultivated rice increased significantly. Among them, the increased of mda content in leaves and roots of HEB07-2was significantly smaller than that of the other tested materials, and the superoxide anion radical production rate of it was the slowest, significantly smaller than the other tested materials, which indicated that the cell membrane HEB07-2was more complete and was injured less. Thus, under drought stress, HEB07-2had less accumulation of reactive oxygen species and lower degree of lipid peroxidation; Under normal conditions, each test material had similar activity of antioxidant enzymes, which was slightly lower in upland rice IRPARG Under tihe influence of drought stress, leaves and roots of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR), dehydroascorbate reductase (DHAR) activity increased significantly and the non-enzymatic antioxidants glutathione and ascorbic acid content also increased significantly. However,72hours later, the antioxidant enzyme activity and antioxidant content of drought-sensitive varieties decreased, while the increase rates of the upland rice IRPARG and WR04-6less than that of HEB07-2, which indicated that HEB07-2can effectively scavenge the excessive production of reactive oxygen species (ROS) to ease drought stress damage to the biological membrane. Leaf and root osmotic adjustment of HEB07-2was significantly increased by the impact of drought stress, and leaves and roots soluble sugar showed an earlier increase and later decrease. The increase of osmotic adjustment substances in WR04-6and IRPARG was smaller than that in HEB07-2, which indicated that under drought stress, HEB07-2can maintain cell water potential by accumulating more osmotic adjustment substances, so as to achieve the purpose of the drought resistance.72h after the PEG simulated drought stress, total chlorophyll conten tin drought-sensitive varieties significantly reduced, while the chlorophyll content of HEB07-2increased. Total chlorophyll contentin WR04-6and Brazilian Upland did not change significantly. During drought stress, initial fluorescence (Fo) increased, while the maximum fluorescence (Fm) decreased. Drought-sensitive variety Yuefu had the highest increase. While the beginning time of Fo increased and decreased of Fm was later than others’, which indicated that HEB07-2was injured later than others. The net photosynthetic rate and stomatal conductance were decreased due to drought stress. Among them, drought-sensitive variety Yuefu had the highest decrease of net photosynthetic rate and stomatal conductance, while HEB07-2had the lowest decrease. Groups temperature changes was determined by infrared camera measurement, leaf temperature in Yuefu and WR04-6increased significantly under drought stress, while leaf temperature in HEB07-2and upland rice IRPARG had no significant change.Comparative analysis of terminal drought tolerance weedy rice HEB07-2between drought tolerance upland rice IRPARG by using expression profiles showed that the response to drought of transcriptome of weedy rice HEB07-2between upland rice IRPARG had significant difference in the respects of response directions and degrees. The majority of genes expressed in HEB07-2were most up-regulated, while in IRPARG were down-regulated, and the fold change of HEB07-2genes were larger. Gene ontology(GO) analysis suggested that weedy rice HEB07-2and upland rice IRPARG three categories of differently expressed genes related to biological process, cell component, molecular function, can be verified with physiological indexes. |
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