Reversion of deleterious effects of salt stress by activation of ROS detoxifying enzymes via foliar application of 24-epibrassinolide in rice seedlings

We evaluated the effects of foliar application of 24-epibrassinolide (EBL) on growth, oxidative metabolism and water relations of rice seedlings cv. J-104, stressed with 100 mmol L−1 NaCl for 7 days and recovered without NaCl in the nutrient solution during the next 15 days. Measurements were made at the beginning, at the end and after recovery from salt stress. Salinity decreased growth but the effects were observed during the recovery period. Foliar application of EBL restored growth in salt stressed seedlings. Water relations were affected by salt stress but spraying EBL only restored turgor potential. Proline concentration increased after recovery in salt stressed seedlings and application of EBL reverted this effect by 35 %. Lipid peroxidation and protein oxidation increased with salt stress and seedlings sprayed with EBL showed lower damage to membranes and proteins than salt stressed plants without EBL application. Antioxidant enzymes responded variably to salt stress, peroxidases and SOD either decreased or were little affected by salt stress, whereas catalase activity increased with salinity. The effect of EBL on antioxidant enzymes was in general to increase activities of catalase, ascorbate peroxidase and SOD. The protective effects of EBL of salt stressed rice seedlings may be associated with a decrease of oxidative stress probably modulated by proline accumulation via catalase and SOD, evidenced by a reduction of lipid peroxidation and proteins oxidation, and maintenance of chlorophylls concentration.