Effect of 28-homobrassinolide on photosynthesis, fluorescence and antioxidant system in the presence or absence of salinity and temperature in Vigna radiata

The plants of Vigna radiata c.v. T-44 were supplemented with 28-homobrassinolide (HBL) both in the presence or absence of high temperature and/or NaCl and were sampled, 18 days after sowing (DAS). The plants exposed to high temperature and/or NaCl exhibited a significant decline in growth, photosynthetic parameters and a maximum quantum yield of PSII. However, the follow up treatment with HBL detoxified the stress generated by high temperature and/or NaCl and significantly improved the values for the above parameters. The high temperature and/or NaCl increased electrolyte leakage and lipid peroxidation, and decreased the membrane stability index (MSI) and leaf water potential (ψ). However, HBL treatment, in the absence of stress, improved the MSI and leaf water potential (ψ) but could not influence electrolyte leakage and lipid peroxidation. The antioxidative enzymes and the level of proline exhibited a significant increase in the response to HBL as well as to high temperature and/or NaCl stress.