Brassinosteroids (BRs) are considered to possess protective activity in plants exposed to various stresses. The present study was conducted to evaluate the effects of 24-epibrassinolide (EBL) on salt stressed summer squash cv. Eskandrani seedlings, whether it can alleviate the deleterious effects of salt stress in growing seedlings or not. For this, summer squash seeds were germinated in solidified half strength MS (Murashige and Skoog) medium supplemented with different concentrations and combinations of EBL (0, 5, 10 and 20 μM) and NaCl (0, 50, 100 and 150 mM). The different concentrations (5, 10, 20 μM) of EBL significantly increased germination percentage and seedling growth capacity and the greatest increase was observed at 10 μM EBL. EBL application significantly increased the contents of photosynthetic pigments, the relative water content and the uptake of K and Ca. However, the different concentrations (50, 100 and 150 mM) of NaCl significantly decreased the above-mentioned attributes. The different concentrations (50, 100 and 150 mM) of NaCl significantly increased the electrolyte leakage, the lipid peroxidation and the Na uptake, but the interaction between EBL and NaCl significantly decreased these parameters. The results of this study proved that the application of 24-epibrassinolide to growing squash seedlings under salt stress conditions reduced the deleterious effects of salt stress and increased the tolerance of seedlings to its detrimental effects.
Keywords: 24-epibrassinolide; Squash; electrolyte leakage; lipid peroxidation; salt stress.