Epibrassinolide confers zinc stress tolerance by regulating antioxidant enzyme responses, osmolytes, and hormonal balance in Solanum melongena seedlings

Brassinosteroids have been widely applied to confer plant resistance to various stresses. The objective of this study was to evaluate the role of exogenous epibrassinolide (EBL) in some physiological processes in the leaves of eggplant ( Solanum melongena L.) seedlings grown under zinc (Zn) stress conditions. Exposure to 10 mM Zn treatment for 8 days led to an inhibition of eggplant growth, a decrease in chlorophyll level, and an aggravation of oxidative damage. Exogenous spray of 0.1 µM EBL dramatically alleviated oxidative damage caused by excess Zn, as shown by decreases in the levels of malondialdehyde and superoxide anion, and increases in plant growth, chlorophyll content, and antioxidant enzyme activities of superoxide dismutase, guaiacol peroxidase, catalase, and ascorbate peroxidase in the leaves of eggplant seedlings under Zn stress. It was also observed that osmolytes such as soluble sugars and free proline were further increased in EBL plus Zn-treated eggplant seedlings. Furthermore, EBL treatment alone or in combination with Zn stress significantly enhanced indole-3-acetic acid and zeatin riboside contents, while a sharp increase in abscisic acid content was recorded for EBL application under Zn stress. Results in the present work revealed that EBL greatly alleviated harmful effects of Zn stress on eggplants by activating antioxidant enzyme responses, accumulation of osmolytes, and balancing endogenous hormones.