Mechanism Of Exogenous Betaine On Improving Salt Tolerance Of Suaeda Salsa

Suaeda salsa（S.salsa）plays a crucial role in the natural succession of the Liaohekou Coastal Wetland,which is the largest wetland in northern China.Unfortunately,the wetland’s ecological environment has been significantly damaged in recent years due to human coastal activities and environmental issues,leading to the degradation of the S.salsa community.Research has shown that higher salinity is one of the reasons for the degradation of S.salsa,which affects the osmotic regulation inside the plant and thus affects its distribution.Glycine betaine（GB）is a widely distributed quaternary ammonium compound in microorganisms and plant and animal cells,which has a role in osmotic regulation and protection.Therefore,this study used S.salsa from Panjin Coastal Wetland as the research object and applied seawater to simulate the wetland salt environment for potted cultivation experiments.Under seawater stress,different concentrations of GB（0mmol/L,10mmol/L,30mmol/L,and 50mmol/L）were applied To investigate the effects of exogenous GB on S.salsa growth and metabolism from multiple aspects such as antioxidant system,osmotic regulation system,amino acid metabolism,and fatty acid metabolism.The aim of this article is to provide a reference for ecological restoration and reconstruction techniques of the S.salsa community in the Liaohekou wetland and to evaluate the feasibility of using exogenous betaine in S.salsa wetland restoration.The study concludes that:（1）Under seawater stress,the plant height,weight and relative moisture content of S.salsa decreased,and after applying different concentrations of exogenous GB,the plant height,weight,and relative water content of S.salsa significantly increased.This indicates that seawater stress inhibits the growth of S.salsa,while exogenous GB has a positive promotion effect on its growth.Notably,30 mmol/L GB exhibits the strongest promotion effect on S.salsa growth.（2）Sea water stress inhibits the accumulation of photosynthetic pigments in S.salsa,while promoting the increase of soluble sugar content and reducing the content of soluble protein.The application of different concentrations of exogenous GB promotes photosynthesis of S.salsa.Low concentrations of GB promoted the accumulation of soluble sugars and proteins,while high concentrations of GB inhibited the accumulation of soluble proteins in S.salsa.（3）Applying different concentrations of exogenous GB significantly reduces the content of MDA and H₂O₂ in S.salsa,while increasing the activity of antioxidant enzymes SOD,POD,and CAT,thereby improving the antioxidant capacity and reducing the degree of membrane lipid peroxidation.（4）The application of different concentrations of exogenous GB inhibits the transport of Na⁺and K⁺to the aboveground,maintaining the ion homeostasis of S.salsa aboveground.The increase in choline content and enzyme activity of PEAMT,CMO,and BADH in S.salsa promotes the synthesis of endogenous GB,increases the total GB content in the roots,stems,and leaves of S.salsa,and enhances the plant’s osmotic regulation ability.（5）Applying different concentrations of exogenous GB significantly increases the content of various amino acids in the roots,stems,and leaves of S.salsa,promoting the synthesis of amino acids in the plant.（6）Applying different concentrations of endogenous GB significantly increases the content of unsaturated fatty acids in the roots,stems,and leaves of S.salsa,increasing the fluidity of its biofilm and reducing the degree of membrane lipid peroxidation.In addition,after applying different concentrations of endogenous GB,the value ofδ¹³C in the roots,stems,and leaves of S.salsa significantly increases,indicating that GB can change the carbon composition in fatty acids,particularly by increasing the utilization ratio of ¹³C in low-carbon fatty acid synthesis.The research findings suggest that applying exogenous GB can effectively enhance the growth of S.salsa,providing a crucial theoretical foundation for the restoration of the S.salsa community in the Liaohe Estuary wetland.