Mechanism of high temperature resistance induced by application of Epi-brassinolide in tomato seedling.

In the present study,tomato seedlings(with four leaves),grown in pots,were sprayed with different grades of epi-BR concentrations(0,0.01,0.05,0.10,0.50,1.00,1.50 mg / L),twice at two days interval followed by high temperature stress(40℃) for 24h.The MDA,proline contents and relative conductivity in leaves were determined after stress to evaluate suitable epi-BR concentration for inducing resistance to high temperature.The screened epi-BR concentration was sprayed to the leaves of tomato seedlings,and the seedlings were treated with high temperature stress(40℃).The activities of SOD,POD,CAT and APX and the contents of superoxide radical and H2O2 were determined at 0,3,6,12 and 24 h of the stress to study the mechanism of high temperature resistance in tomato seedling.The results showed that the best epi-BR concentration in inducing resistance to high temperature was 0.5 mg / L.Spraying 0.5 mg / L epi-BR could maintain high activities of SOD,POD and APX in leaves under stress,reduce the production and accumulation of active oxygen,reduce the membrane lipid peroxidation,enhance the stabilization of cell membrane and improve the resistance to high temperature in tomato seedlings.