Effects of 24-Epibrassinolide and Its Conjugate with Succinic Acid on the Resistance of Rapeseed Plants to Chloride Salinization

Exogenous 24-epibrassinolide (EBL) and a synthetic EBL-based conjugate (2,3,22,23-tetraester of EBL and succinic acid) used at 10 nM were for the first time shown to almost equally mitigate the negative effects of salt stress (150 mM NaCl) on rapeseed plants, sustaining their photosynthetic activity and growth parameters. Specificity was observed in the action of the compounds in regulating the NaCl resistance of rapeseed plants. EBL increased the content of carotenoids and superoxide dismutase and peroxidase activities in plants exposed to chloride salinization, while the EBL conjugate increased peroxidase activity only. Pretreatment of plants for 4 h before stress exposure was more efficient than treatment applied simultaneously with stress.