Mechanism Of Exogenous Ca²⁺ Alleviating The Injury Of Siberian Nitraria Pall.Induced By Salt Stress

Nitraria sibirica Pall.is a halophyte of the Nitraria genus Nitraria.It has strong drought resistance,cold resistance,barren resistance,salt and alkali resistance,wind and sand resistance,and has high forage and medicinal value.The ecological benefit and economic benefit are equal,and it is one of the ideal tree species to control land salinization,desertification,wind and slope protection.The effects of exogenous Ca²⁺on reactive oxygen species metabolism,As A-GSH circulatory system,endogenous hormone content and transcriptome of Nitraria sibirica under salt stress were studied by soilless cultivation with nutrient solution.The following conclusions were obtained:(1)The relative water content of leaf of Nitraria sibirica under salt stress decreased significantly,and the applied Ca²⁺increased the relative water content of leaf of Nitraria sibirica under salt stress.Chlorophyll content of Siberian white thorn leaves decreased significantly under moderate stress salt concentration,and the addition of Ca²⁺could promote the synthesis of chlorophyll in Nitraria sibirica under normal growth conditions and salt stress conditions.(2)The content of O₂^?-,H₂O₂ and MDA in leaves of Nitraria sibirica under salt stress increased significantly;Ca²⁺can reduce the production rate,H₂O₂ content and MDA content of O₂^?-under salt stress,The production rate and MDA content of the O₂^?-returned to the same level as the control group;The activities of SOD and CAT in leaves of Nitraria sibirica were significantly increased under salt stress,Compared with the control group,the activity of POD had no significant change.The addition of exogenous Ca²⁺increased the activity of SOD?POD?CAT in leaves of Nitraria sibirica under salt stress;Salt stress significantly increased the activities of APX and MDHAR in leaves of Siberian white thorn;significantly reduced reductive As A content and DHAR activity.exogenous Ca²⁺significantly increased antioxidant As A?reduced GSH content and antioxidant enzymes DHAR?GR,APX,MDHAR activity,and As A/DHA,GSH/GSSG ratios in Nitraria sibirica leaves under salt stress.Description,The exogenous Ca²⁺can increase the antioxidant enzyme activity and the As A and GSH content of antioxidant substances in Siberian white thorn leaves under salt stress,Enhancing the ability of the As A-GSH cycle to remove reactive oxygen species,To alleviate the oxidative damage of salt stress to Siberian white thorn.(3)The content of abscisic acid(ABA)in leaves of Nitraria sibirica under salt stress increased significantly,the contents of auxin(IAA)and gibberellin(GA)decreased significantly.The application of exogenous Ca²⁺could alleviate the adverse effects of ABA accumulation of Siberian White Spurs on plants under salt stress,and increase the content of IAA and GA alleviated the problem of reducing the growth activity caused by salt stress.(4)There were 45 genes differentially expressed in the leaves of Nitraria sibirica compared with those of exogenous Ca²⁺under normal conditions.There were 256 differentially expressed genes in Na Cl treatment group and Na Cl and Ca²⁺treatment group.Gene function analysis found that these differentially expressed genes Ca²⁺regulate the response of Nitraria sibirica to salt stress were mainly enriched in redox process,response to water stress,chloroplast,vacuole-redox-enzyme activity and so on.During salt stress,the addition of exogenous Ca²⁺made the whole Nitraria sibirica transcriptome tend to return to the control group level.