Effects Of Exogenous Salicylic Acid And Abscisic Acid On Growth And Physiological Characteristics Of Medicago Polymorpha Under High Temperature Stress

Medicago polymorpha L.is rich in nutrients and can be used for feed,green manure,vegetable,medicinal and other purposes.It is a rare and versatile forage.Medicago polymorpha mainly grows in the south of the Yangtze River Basin in my country.It is very sensitive to high temperature environment and is vulnerable to high temperature stress.How to improve the ability of Medicago polymorpha to resist high temperature has become an urgent problem in production.For this reason,this study selected Medicago polymorpha as the test material to explore the effects of different concentrations of salicylic acid,abscisic acid and their combined treatment on the growth and physiology of Medicago polymorpha under high temperature stress(38℃/30℃(day temperature/night temperature)).The main research conclusions are as follows:1.High temperature stress will damage the growth and physiology of Medicago polymorpha.Compared with the control group,the plant height,aboveground biomass,chlorophyll content and soluble protein content of Golden Cauliflower under high temperature stress were significantly reduced(P<0.05),membrane lipid peroxidation occurred in the cell membrane,and MDA content and relative conductivity increased significantly(P<0.05),the growth of Medicago polymorpha was significantly inhibited.2.Foliar spraying of 2.5 mmol/L SA under high temperature stress can significantly increase the aboveground biomass,fluorescence parameters Fm and Fv/Fm values of Medicago polymorpha(P<0.05).Significantly reduce the relative conductivity and MDA content(P<0.05).In addition,CAT activity,soluble sugar content and soluble protein content were significantly increased(P<0.05).3.Foliar spraying 54 mmol/L of ABA under high temperature stress can significantly increase the aboveground biomass,total chlorophyll,soluble sugar and soluble protein content of Medicago polymorpha(P<0.05)),increase the value of chlorophyll fluorescence parameters Fm and Fv/Fm,reduce the relative conductivity,significantly reduce the MDA content(P<0.05),and the antioxidant enzyme SOD and CAT activities are also significantly increased(P<0.05).4.Under high temperature stress,the combined treatment of SA+ABA(2.5 mmol/L+54 mmol/L)improves the chlorophyll content,SOD and POD activity of Medicago polymorpha better than single SA(2.5 mmol/L)or ABA(54 mmol/L)treatment,the MDA content and relative conductivity under the combined treatment are also lower than single SA(2.5 mmol/L)or ABA(54 mmol/L)treatment,and the soluble protein and soluble sugar content under the combined treatment are higher than single SA(2.5 mmol/L)or ABA(54 mmol/L)treatment.In summary,the addition of 2.5 mmol/L SA or 54 mmol/L ABA can alleviate the harmful effects of high temperature stress on Medicago polymorpha,and the effect of SA+ABA combined treatment will be better.The conclusions of this study provide a theoretical basis for using SA or ABA to alleviate the harmful effects of high temperature stress on Medicago polymorpha.