Physiological Responses And Citrate Synthase Mechanism Of Sinapis Alba Under Drought Stress

The purpose of this study was to study the physiology and biochemistry response and citrate synthase gene expression of Sinapis alba seedling under drought stress. We adopted soil culture and PEG6000simulating drought stress. We had three concentration of PEG which were10%,15%,20%, there were four concentration adding CK group. In addition to there were the different time treatment gradient design, which were3days,6days,9days, and12days respectively, based on the different time of taking leaves. The experimental materials is drought resistance breed white mustard one. The physiology and biochemistry response were studied by the measurement of the chlorophyll content, the content of soluble sugar, soluble protein content, MDA and SOD, CAT, POD enzyme activity of white mustard leaves. The citrate synthase gene expression was researched through the fluorescent quantitative PCR results of gene in white mustard leaves under15%and20%PEG condition and different time.Under different concentration and different drought stress time, the external feature of white mustard had enomous differences with CK group. The stem became thinner and weaker and the plant wilted, leaves became soft and prolapsed. The bottom leaves began to become yellow firstly, and some completely withered seriously. Under drought condition, the chlorophyll content dropped contrasted to control group; the soluble sugar and soluble protein content was on the trend of decline after rising first as time continuoued and the increase of the concentration; the content of MDA showed a rising trend all the time. This three indexes showed that the plants resisted drought stress through the increase of the content of the materials. Under drought condition, the activity of the three kinds of oxidoreductase(SOD, CAT and POD) was on the trend of decline after rising basically. SOD and POD is both rises before the fall, but CAT did not change significantly, which was different.Which can be seen from citrate synthase gene expression is that white mustard accommodated environmental changes through the increase of gene expression, then the plant gradually adapted to the environment and recovered. Under severe drought stress, the expression did not fall after the rise. That is indicated that the plant physiological damage can not recover any more. From the change of citrate synthase gene expression under drought stress, we can indirectly judge the way in which Krebs cycle in the drought stress react. This is significant to the study of reaction and the synthesis and decomposition of sugar and fatty acid metabolism of plant under the adverse situation.