Study Of Physiological Mechanism Of Exogenous ?-tocopherol On Improving The Salt Tolerance Of Carex Leucochlora

Soil salinity severely affects the growth and development of plants.It is important to reduce the damage of salt-stress to plants with chemical method,promote the adaptability to salted environment,and strengthen the greening of saline land.?-Tocopherol is one of the important lipid-soluble antioxidants and cell membrane effectors in the adversity.We studied the effects of exogenous applied ?-tocopherol on the growth inhibition of Carex leucochlora under salt stress?0.8% NaCl?.On the basis of above,the effects of ?-tocopherol on reactive oxygen species metabolism,photosynthesis and osmotic adjustment metabolism in C.leucochlora under salt stress were also studied.The aim of this study was to reveal the main physiological effects of exogenous ?-tocopherol and provide a certain theoretical basis in improving the salt tolerance of plants.Main results were as follows:1.Suitable concentration exogenous ?-tocopherol could alleviate the inhibitory effect of salt stress on growth and plasma membrane of C.leucochlora.0.2m M-1.0m M ?-tocopherol improved the plant height and dry matter accumulation of C.leucochlora under salt conditions,decreased malondialdehyde?MDA?content and relative membrane permeability.Among these results,the 0.8m M ?-tocopherol treatment showed the best effect.Moreover,foliar spraying 0.8m M ?-tocopherol significantly increased the total content of endogenous tocopherol in plants.2.Exogenous ?-tocopherol application significantly reduced the excess accumulation of reactive oxygen species in plants by increasing the activities of antioxidant enzymes and improving the ascorbate-glutathione cycle.Salt stress significantly increased reactive oxygen species level,superoxide dismutase?SOD?and catalase?CAT?activities,ascorbic acid?ASA?and glutathione?GSH?contents of C.leucochlora,while the ratio of ASA/DHA and GSH/GSSG were significantly decreased.After spraying ?-tocopherol,the activities of SOD,peroxidase?POD?and CAT were increased.In addition,the contents of non-enzymatic antioxidants such as ASA and GSH,the ratio of ASA/DHA and GSH/GSSG,APX,GR and DHAR activities were significantly increased as well.Therefore,it showed that exogenous ?-tocopherol could clear the ROS caused by salt stress by increasing the activities of antioxidant enzymes and the content of non-enzymatic antioxidants in ascorbate-glutathione cycle.In this way,it could lessen the damage to C.leucochlora caused by the salt stress.3.Exogenous ?-tocopherol significantly improved the osmotic regulation of C.leucochlora under salt stress.The ratio of K⁺/Na⁺,Ca²⁺/Na⁺ were decreased;the free proline and soluble sugar content were increased significantly,while soluble protein content increased first and then decreased.Moreover,the K⁺/Na⁺ and Ca²⁺/Na⁺ values were significantly increased by exogenous ?-tocopherol under salt stress.In comparison with Na Cl alone,the 0.8 m M ?-tocopherol application significantly increased the content of free proline and soluble protein,but had no effect on the content of soluble sugar.Therefore,these results showed that exogenous ?-tocopherol could maintain the equilibrium osmotic pressure and ion ratio by adjusting the inorganic and organic osmotic adjustment substances in plants.4.Exogenous ?-tocopherol significantly improved the photosynthetic performance of C.leucochlora under salt stress.With the decreasing of chlorophyll content and stomatal conductance?Gs?,the net photosynthetic rate?Pn?was also decreased under salt stress.Salt stress significantly reduced the actual photochemical efficiency??PS??of PS?,the highest potential photochemical efficiency?Fv/Fm?and photochemical quenching coefficient?q P?of PS?,while the initial fluorescence value?Fo?was increased.?-Tocopherol could increased chlorophyll b and carotenoid content of C.leucochlora.In addition,?PS?,q P and Gs values were also improved.The results showed that the chlorophyll PS? reaction center of C.leucochlora was destroyed,the photosynthetic performance was decreased under salt stress.Exogenous ?-tocopherol could increase the actual photochemical efficiency to strengthen plants' salt tolerance by enhancing the transport rate of photosynthetic electron and light sharing distributed by photochemical reaction to enhance the salt tolerance of C.leucochlora.