The Mitigation Effect Of Exogenous SA、Ca²⁺、K⁺ Under Na Cl Stress Of Acer Truncatum

With the chlorine salt snow-melting agent is widely used in winter snow clearing,more and more attention has been paid to the harm of snow-melting agent to plants and even the environment.Snow-melting agent makes street trees and landscape plants along suffer from different degrees of salt ingury,which seriously affects the ornamental effect and normal growth and development of landscape plants.A.truncatum was used as the experimental material,three exogenous substances SA、Ca Cl₂ and KCl were added under NaCl stress,objective to explore the effects of exogenous SA、Ca²⁺and K⁺on photosynthetic characteristics、osmotic adjustment、ion absorption and distribution of A.truncatum under NaCl stress,so as to clear the mitigation effect of three exogenous substances on A.truncatum under NaCl stress,and screening of the better exogenous substances.The main results of this study are as follows:During the whole experimental period,the net photosynthetic rate、transpiration rate、stomatal conductance、intercellular CO₂ concentration and chlorophyll content of A.truncatum were significantly decreased,the content of MDA、soluble sugar、soluble protein and the activity of CAT and POD were significantly increased,the content of Na⁺in leaves was significantly increased,the content of K⁺、Ca²⁺、Mg²⁺were significantly decreased,and the K⁺/Na⁺、Ca²⁺/Na⁺and Mg²⁺/Na⁺were decreased.Exogenous SA、Ca²⁺and K⁺were significantly alleviated the photosynthesis inhibition、membrane peroxidation and ion antagonism of A.truncatum under NaCl stress,improved the photosynthesis of A.truncatum（net photosynthetic rate、transpiration rate、stomatal conductance、intercellular CO₂ concentration）,the content of photosynthetic pigment（chlorophyll a、chlorophyll b、chlorophyll a+b）,osmotic adjustment substances（soluble sugar、soluble protein）,antioxidant enzyme activity（CAT、POD）.Promoted the absorption of K⁺、Ca²⁺and Mg²⁺,inhibited the absorption of Na⁺,and increased K⁺/Na⁺、Ca²⁺/Na⁺、Mg²⁺/Na⁺of leaves.Exogenous SA and Ca²⁺had significantly alleviated each photosynthetic parameters、photosynthetic pigment、osmotic adjustment substances content and antioxidant enzyme activity of A.truncatum under NaCl stress during the whole stress period.Exogenous K⁺only had significantly mitigation effect in the early stage of stress,and there was no significantly difference in the later stage.Compared with the three exogenous substances,the net photosynthetic rate、Stomatal conductance、intercellular CO₂ concentration、POD activity、Mg²⁺content of A.truncatum were improved,the MDA、Na⁺content of A.truncatum under NaCl stress were reduced,exogenous SA and Ca²⁺had better significantly mitigation effect than those of exogenous K⁺at stress 36 day.In conclusion,exogenous SA、Ca²⁺and K⁺were reduced the photosynthetic inhibition of A.truncatum under NaCl stress,improved the osmotic adjustment ability,regulated the ion balance,alleviated the damage of A.truncatum under NaCl stress,maintained the normal growth and development of A.truncatum and improved the salt tolerance.Compared with the mitigation effect,exogenous SA and Ca²⁺had better mitigation effect of A.truncatum under NaCl stress than exogenous K⁺.