表油菜素内酯诱导番茄幼苗抗高温机理的研究

采用表油菜素内酯叶面喷施处理番茄幼苗，通过测定丙二醛、脯氨酸、相对电导率3个生理指标，筛选出诱导番茄幼苗抗高温的最佳浓度，并利用此浓度探讨表油菜素内酯诱导番茄幼苗抗高温的能力及机制。结果表明，表油菜素内酯诱导番茄幼苗抗高温（40℃）的最佳浓度为0．50mg／L；其诱导番茄幼苗耐热性的作用机理主要在于：喷施处理后，在高温胁迫条件下能够维持番茄幼苗有较高的SOD、POD、APX活性，有效降低活性氧（O2^-·和H2O2）的产生和积累，减少膜脂过氧化的产生，从而保护细胞膜的热稳定性，提高番茄幼苗的抗高温能力；在提高番茄幼苗耐热性作用中，CAT活性是高温胁迫响应的原因之一，但表油菜素内酯诱导番茄幼苗抗高温能力可能与CAT的活性无关。

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.