Effects of 2,4-epibrassinolide on the growth and physiological characteristics of Phaseolus vulgaris seedlings under saline and alkaline stresses

Abstract

Abstract [Objective] The study aims to explore the physiological mechanism of exogenous 2,4-epibrassinolide (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 conductivity (REC), malondialdehyde (MDA) content, and intercellular CO2 concentration (Ci) were significantly 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 reduced 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 substance 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 enhances the salt-alkali resistance of common bean seedlings.

Keywords

• phaseolus vulgaris l.
• saline-alkali stress
• 2 4-epibrassinolide(2 4-ebr)
• brassinazole (brz)
• photosynthesis
• osmotic regulation
• antioxidant enzyme