Concentration effects and its physiological mechanism of soaking seeds with brassinolide on tomato seed germination under salt stress

The effects of seed soaking with 10-11, 10-10, 10-9, 10-8, 10-7, 10-6, and 10-5 mol/L 2, 4-epibrassinolide（EBL） on the germination, growth, solute accumulation and antioxidant metabolism of tomato seeds under 0, 50, 100, 150, and 175 mmol/L NaCl stress for 7 days were studied to reveal the effect and mechanism of brassinosteroids on improving salt tolerance of crops. The results showed that 10-9 mol/L EBL soaking seeds could significantly promote the germination of tomato seeds under comparative higher salt stress of NaCl concentration. Under all treatments, excessive high EBL concentrations(10-6 and 10-5 mol/L EBL) of soaking seeds showed inhibition effect on tomato seed germination. After seed germination under salt stress, seed soaking with a certain concentration of EBL could significantly increase the length of the seed radicle and hypocotyl, the fresh weight of seedlings and seed vigor index, among which 10-9 mol/L EBL seed soaking treatment had the optimum promotion effect, while seed soaking treatment