Effects of exogenous brassinolide and AM fungi on growth, photosynthetic characteristics and antioxidant enzyme system of Leymus chinensis under salt and alkali stress

Salinity and alkali stresses are a major abiotic stress negatively affecting crop productivity around the globe. Therefore, it is mandatory to develop the effective measures to mitigate the adverse impacts of these stresses for ensuring sustainable crop productivity and food security. Therefore, a pot experiment determined the effects of brassinolide application, inoculation with AM fungi (Funneliformis mosseae) and their combined use on the growth, photosynthesis and antioxidant system of Leymus chinensis under saline-alkali stress (0, 150 mmol/L). The mechanism of the two to alleviate the saline-alkali stress of L. chinensis was explored. The physiological and biochemical indexes of Leymus chinensis were significantly affected under saline-alkali stress (150 mmol/L). Inoculation of AM fungi and application of brassinolide effectively increased the biomass accumulation in the upper part (∼ 25-40%) and root (15-35%) system of L. chinensis under saline-alkali stress. Further AMF also improved   photosynthetic pigments (chlorophyll a, chlorophyll b), photosynthetic rate (Pn), Intercellular CO2 concentration (Ci), stomata conductance (Gs), transpiration rate (Tr), chlorophyll fluorescence antioxidant enzymes (SOD: superoxide dismutase. CAT: catalase APX: ascorbate peroxidase, GR: Glutathione reductase) activity, and decreased malondialdehyde (MDA: ∼ 40-50%) and hydrogen peroxide (H2O2: ∼ 30-40%) accumulation. Therefore, under saline-alkali stress conditions, the combination of brassinolide and AM fungi proved better to mitigate their toxic effects.