Effects of 2,4-epibrassinolide on the growth and physiological characteristics of Phaseolus vulgaris seedlings under saline and alkaline stresses
[Objective]The study aims to explore the physiological mechanism of exogenous 2,4-epibrassin-olide(2,4-EBR)in alleviating the damage caused by salt-alkali stress in common bean(Phaseolus vulgaris L.)seedlings,to provide a basis for the application of 2,4-EBR to alleviate salt-alkali stress in leguminous plants.[Methods]Using Shanxi red common bean'Yunxuan 2'as the test material,the authors studied the effects of exogenous spraying of 0.1 mg/L 2,4-EBR and 4.0 mg/L brassinozole(BRZ)on the growth,photosynthetic gas parameters,antioxidant enzyme activity,and osmotic adjustment substance of common bean seedlings under saline-alkali stress at 100 mmol/L.[Results]Under saline-alkali stress,common bean leaves were curled and withered,and plant height,leaf area,main root length,synthetic pigment content,net photosynthetic rate(Pn),transpiration rate(Tr),and stomatal conductance(Gs)were all decreased significantly(P＜0.05),proline(Pro),soluble sugar(SS)content,and superoxide dismutase(SOD),peroxidase(POD),catalase(CAT),and ascorbic acid peroxidase(APX)activities,relative con-ductivity(REC),malondialdehyde(MDA)content,and intercellular CO2 concentration(Ci)were signifi-cantly increased.Exogenous spraying of 2,4-EBR alleviated the wilting and curling of leaves caused by salt-alkali stress,and the plant growth condition was gradually improved.Meanwhile,it effectively re-duced the REC,MDA,and Ci in the leaves of the seedlings,and significantly increased plant height,leaf area,primary root length,Pro,SS,Pn,Tr,and Gs as well as SOD,POD,CAT,and APX activities.These salt-alkali resistant effects of common beans induced by exogenous 2,4-EBR were reversed by adding BRZ.[Conclusion]Exogenous 2,4-EBR treatment can reduce membrane lipid peroxidation damage caused by salt-alkali stress by increasing antioxidant system enzyme activity and osmotic adjustment sub-stance content in common bean.It effectively removes the non-stomatal limiting factors that weaken the photosynthesis of common bean seedlings under saline-alkali stress,promotes seedling growth,and en-hances the salt-alkali resistance of common bean seedlings.
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