The Function Of Photorespiration And Antioxidative System In Caragana Korshinskii Kom. Tolerance To Drought Stress

Drought stress would destroy the redox homeostasis or induce metabolic disorders,and was the major factor limited plants growth and crop productivity.Photorespiration is the core metabolism in plants,and could prevent photoinhibition and photo-oxidative stress by many mechanisms under drought stress.Antioxidative could effectively eliminate ROS and improve plants tolerance to drought stress. However,the relative contribution of photorespiration and anti-oxidative systems in plants adapting to drought and the relationship between them are still unclear.Caragana korshinskii Kom.with characteristic of tolerance to stressful conditions extensively distributes arid and semi-arid area,and is the primary species of ecological restoration in this region.In recent years,the plant is gradually becoming a model plant to investigate the drought adaptation.However,the researches concentrated on physiological adaptation in C. korshinskii.And little study was reported about the effect of drought stress on metabolism.Present research had selected the C.korshinskii from different drought level areas in Loess Plateau as the target materials,and investigated the metabolic,physiological and biochemical as well as molecular responses to water stress.The major results as following:（1） Using NMR detected the metabolites content in C.korshinskii leaves.Principal component analysis and Partial least squares discriminant analysis results suggested drought stress had great influence on C.korshinskii metabolism;Pathway analysis indicated the significant metabolic pathways under different drought levels were the glutathione metabolism as well as glycine,serine and threonine metabolism.（2） Detecting gas exchange and fluorescence parameter calculated the photorespiratory rate.The result suggested that phororespiratory rate elevated under drought stress;Enzymes and qPCR results suggested drought induced the up-regulation of gene expression and activity of key enzymes;In addition, glutamate and glyoxylate content significantly increased. These results suggested drought induced the up-regulation of photorespiratory gene expression and then elevated photorespiratory rate.（3） GSH and AsA content markedly increased under drought stress.In addition,the relative expression of major antioxidative enzymes gene significantly up-regulated.However,the enzymes results indicated the catalase activity gradually decreased,ascorbate peroxidase and superoxide dismutase activity steadily increased,glutathione reductase activity presented“first decrease and then increase”. In addition,correspondence analysis suggested the generation of GSH primarily came from synthesis than reduction of oxidized glutathione under drought stress.In conclusion,under drought stress,photorespiration could effectively prevent ROS generation by consuming electron and energy, and support substrates for glutathione synthesis and maintain photosynthesis by supply substrate to Calvin cycle. In addition,photorespiration and antioxidative system could synergistically improve C.korshinskii tolerance to drought stress. Under relative high rainfall,the catalase is the preponderant mechanism to detoxify H₂O₂; the ascorbate peroxidase and superoxide dismutase as well as photorespiration played major contribution improve adaptation capacity under long-time lower rainfall.