Effects Of Gas Signal Molecule Hydrogen Sulfide On Salt Tolerance Of Grape Seedlings

Currently,25%irrigated land around the word is threatened by salinization.Soil salinization is progressively becoming a global resource and environmental issue,with the sustainable development of agricultural production and ecological environment construction under serious threat.As a major saline land country in the world,a comprehensive management of saline soils,enhancement of plants’ability to resist salt stress,and optimization of the utilization of saline land resources have become essential issues to be tackled in china.As a broadly grown and well-adapted cash crop,grapes are one of the most promising fruit trees to be cultivated on saline lands.Improving the salt resistance of grapes will improve the yield and quality of grapevine in saline land,which is important for the development and utilization of saline land.Hydrogen sulfide（H₂S）,a newly recognized endogenous gas signaling molecule,is involved in a number of physiological and biochemical processes in both animals and plants.Moreover,it has been investigated that low concentrations of H₂S can strengthen plants to resist various abiotic stresses including salt stress.However,the ability of exogenous H₂S to mitigate salt stress injury in grapes has not been in the report.Therefore,in this study,the grapevine"Merlot"seedlings were treated with Na HS（an exogenous H₂S donor）to investigate the effect of H₂S on grape seedlings under salt stress.The main results of the study are as follows.（1）Different concentrations of H₂S donor Na HS solutions were sprayed on grape seedlings under salt stress,it was found that that H₂S could mitigate the salinity damage caused by salt stress,but this alleviation effect had a significant dose effect,with 0.1mmol·L^-1Na HS having the best effect.（2）Exogenous H₂S alleviated the growth inhibition and biomass reduction of aboveground and root parts of grape seedlings exposed to salinity stimuli.Under salt stress,the exogenous H₂S treatment increased grape plants by 52%,48%,69%,32%,47%and 45%in terms of height,root length,above-ground fresh weight,above-ground dry weight,root fresh weight and root dry weight,respectively,all reaching highly significant levels of difference,while water loss was reduced,thus the damaged state of salt stress in grape seedlings were significantly alleviated.（3）Exogenous H₂S treatment increased the light energy utilization efficiency and the photochemical efficiency of photosystem II in leaves of grape seedlings under salt stress.The chlorophyll a,chlorophyll b and carotenoid contents of grape seedling leaves were significantly increased;net photosynthetic rate（Pn）,transpiration rate（Tr）,stomatal conductance（Gs）and water use efficiency（WUE）were significantly increased,carbon dioxide concentration（Ci）was significantly decreased,and the maximum photochemical efficiency（Fv/Fm）and photosynthetic performance index based on absorbed light energy（PIABS）of PSII significantly increased.（4）Exogenous H₂S alleviated the membrane lipid peroxidation of grape seedlings caused by salt stress,alleviated the electrolyte leakage in grape leaves and roots,reduced MDA content in leaves and increased root activity,which played a certain role in maintaining the stability of the cell membrane system.（5）The metabolism of reactive oxygen species in grape seedlings under salt stress was unbalanced,resulting in excessive production of H₂O₂and O₂^·-.The content of antioxidant enzymes（SOD,POD and CAT）and gene expression were increased by spraying Na HS solution on the leaves of grape seedlings.Meanwhile,the content of antioxidants（As A,GSH）and the activity of related antioxidant enzymes（APX,DHAR and MDHAR）in the As A-GSH cycle were increased,which effectively scavenged 27%O₂^·-and 18%H₂O₂,alleviated the oxidative stress caused by salt stress,and helped balance the reactive oxygen metabolic process.（6）Exogenous H₂S can increase the gene expression of H⁺-ATPase and H⁺-PPase of the cell membrane proton pump,activate the gene expression of SOS,SKOR salt resistance pathway and the gene expression of ion transporters HKT2,NHX and CAX,and limit the Na⁺induced by salt stress.Na⁺/K⁺radio was reduced by 22%compared to salt stress alone and the lower Na⁺/K⁺radio was beneficial in maintaining osmotic balance.（7）Exogenous H₂S treatment of grape seedlings under salt stress promoted the degradation of cysteine（Cys）to H₂S by cysteine desulfurase CDes（L-CDes and D-CDes）,which helping increased endogenous H₂S synthesis.H₂S acts as a signaling molecule to transmit salt stress signals and contributes to the activation of salt stress stress response.