The Response Of Plant Respiration To Drought Stress And The Regulation Of Exogenous Substances

In order to probe the leaf respiratory responses to drought stress and regulation of respiration by pyruvate and succinate in plant. In this study, Cerasus humili and Arabidopsis thaliana were used as material, the change of some indicators, for instance respiration, the reduction and oxidation levels of ubiquinone pool, the complex activities of respiration chain in mitochondria and so on were researched under drought stress, the regulation by pyruvate and succinate were also included.As the result of drought stress, the relative water content of leaves(LRWC)decreased rapidly, and the rate of decrease after treatment for0to7days was higher than the rate of it after treatment for7to14days. In comparison to drought treatment, there were no differences in LRWC of treatment by pyruvate and succinate. The LRWC of different treatments could get back to the level of control after rewatered.Under drought stress, salicyldydraxamic acid (SHAM)-resistant cytochrome (Cyt) pathway respiration decreased obviously compared with control plants. Both total respiration and the KCN-resistant SHAM-sensitive alternative (Alt) pathway increased. It was found that exogenous pyruvate and succinate drastically enhanced respiration and increased the rate of Alt pathway respiration after drought treatment for7and14days, respectively.Drought stress resulted in the increase of total content of ubiquinone(UQ), while the increase extent of oxidation more than the extent of reduction. Exogenous pyruvate increased the content of UQ and reduction level, the ratio of reduction level increased dramatically after treatment for7days, and then to14days,all of them decreased dramatically. Exogenous succinate increased the content of reduction level after treatment for14days.There were no salient differences among all kinds of treatments and control for0day. Drought resulted in the activities of complex Ⅰ、Ⅲ、Ⅴ dramatically decreased after treatment for7days and been a little back after treatment for14days. Exogenous pyruvate dramatically increased the activity of complex I after treatment for7days,but to14days, the activity of I was lower than it of other treatment. Exogenous pyruvate dramatically increased the activity of complex II after treatment for7days and dramatically increased the activity of complex I after treatment for14days.In comparison to control, drought treatment resulted in a little decrease of HMP after treatment for7days, but the level of HMP was lower than it of control after treatment for14days. Exogenous pyruvate and succinate increased the ratio of EMP after treatment for7days, and exogenous pyruvate resulted in the ratio of EMP higher than it of TCA. Exogenous pyruvate and succinate dramatically increased the ratio of HMP and made it higher than it of control.The respiration increased with the elevation of temperature as the plant living in normal and drought stress conditions. At high survey temperature, the respiration of control was lower than it under drought stress. Drought stress resulted in decrease of temperature coefficient of cytochrome and alternative respiration.Under drought stress, the ratio of alternative pathway increased and replaced cytochrome pathway to become the prominent respiration. The ratio of reduction level of ubiquinone decreased at drought stress and it also resulted in the activities of all complex decreased in leaves of Arabidopsis thaliana.