Study On Physiological Responses And Mechanism Of Salt Tolerance In New Wheat Varieties

Soil salinization is one of the most harmful abiotic stresses,which seriously damages crops and leads to a significant decline in crop yields.To improve the salinity tolerance of plants is a crucial way to develop and utilize saline-alkali land and environmental governance.Wheat is one of the most important food crops in the world.The current experiment was designed to investigate the response of wheat under salt stress,which is of scientific significance for selecting and breeding of salt-tolerant varieties of wheat and guiding the agricultural development and production of saline-alkali land.The study on the mechanism of salt tolerance in wheat depended on evaluating the innovative wheat genetic materials and varieties.Two wheat varieties with different salt resistance,Xinchun 43（XC43,tolerance）and Xinchun 40（XC40,not tolerance）,were selected to conduct the salt treatment.Such root growth,osmotic regulation,antioxidative capacity and photosynthesis were investigated to explore the physiological mechanism in wheat seedlings in response to salt stress,in order to cultivate new varieties of plants with resistance to salt.The main results are as follows:（1）The aboveground biomass accumulation of XC43 and XC40 decreased significantly under salt stress.The root biomass accumulation of XC43 was significantly reduced under salt stress.The underground biomass of XC43 under low salt(50 mmol L^-1)and medium salt(150 mmol L^-1)treatment was not significantly changed compared with the control group,and the specific root length and specific root area were significantly higher than that of XC40 under each treatment.Under salt stress,the content of mineral nutrient elements in XC43 decreased significantly,but the change in the underground part was less than that in the aboveground part.At the same time,the utilization efficiency of nitrogen and phosphorus increased significantly compared with that of the control in XC43,with significantly higher than that of XC40.（2）Net photosynthetic rate（P_n）of XC40 decreased with the increase of salt concentration and was significantly lower than that of the control,while XC43 showed no significant change under low and moderate concentrations salt stress.Salt stress inhibited the electron transfer rate（ETR）and maximum optical quantum yield（F_v/F_m）in XC40 and XC43,with more inhibition in XC40.The chlorophyll a/b of XC40 decreased significantly with the increase of salt concentration,but there was no significant change in XC43.The chlorophyll content of XC43 was significantly higher than that of XC40 under salt treatment.These results indicated that XC43 can cope with salt stress by stabilizing photosynthetic efficiency under low and moderate concentration salt stress.（3）Salt stress significantly increased the relative conductivity in two wheat varieties,but the relative conductivity of XC43 was significantly less than that of XC40,and the increase of the conductivity of the leaves was greater than that of the roots.The K⁺content in the aboveground part of two wheat varieties decreased significantly under salt treatment,the K⁺content in the underground part of XC43 increased significantly,and there was no change in XC40.And the K⁺/Na⁺ratio in the underground part of XC43 was significantly higher than that in XC40.Under salt stress,the proline content of XC40 and XC43increased significantly,the increment of XC43 was larger,with greater variation in leaves than in roots.（4）Malondialdehyde（MDA）and superoxide anion contents of XC43 and XC40increased significantly under salt stress,with significantly greater in XC40 than in XC43under high concentration salt treatment.Salt stress significantly increased the antioxidant enzyme activities of XC43,especially in roots.The CAT activity of XC43 was significantly higher than that of XC40,and the changes of DHAR and GR activities were greater than that of leaves.Compared with the control,the contents of ASA and GSH in roots of XC43 increased significantly under salt stress and were significantly higher than that of XC40 under high concentration salt treatment.Meanwhile,ASA/DHA and GSH/GSSG in XC43 significantly increased,while XC40 was significantly decreased,indicating that the antioxidant capacity of roots in XC43 was closely related to salt tolerance,and the tolerance to high concentration of salt stress in wheat depended on the antioxidant capacity of the roots.