Effects And Mechanism Of Some Chemicals On The Resistance Induction Of Cucumber Seedlings Against Salt Stress And Botrytis Cinerea Pers. In Greenhouse

Plants are always confronted with all kinds of stress during their whole process of survival, propagation and evolution, which is in fact full of contradiction and coordination between plant and stress. Once the stress surpassed its tolerance capacity, plant would be seriously affected or even die. Each kind of stress, whether biological or abiological stress, often occurred and damaged together, which interacted each other and formed the compound stress.Cucumber (Cucumis sativus L.) is one of the most widely cultivated vegetables in our protected culture. But with the development of protected culture, soil salinization by successive cultivation of single crop and Botrytis cinerea Pers. caused by low temperature, high humidity and light deficiency often occurred together and formed compound stress to badly inhibited the cucumber production and showed a worse trend. Therefore, it's necessary and urgent to explore one economical, environment-protected, simple and fit-to-all method to alleviate the compound damage of multi-stress.In this study, we applied four biotic chemical matters, Salicylic acid (SA), Brassinolide (BR), Chitosan (CTS) and Spermdine (Spd) to study the effects and mechanism of anti-stress by using different concentration of SA, BR, CTS and Spd to induce cucumber seedlings to be resistant against salt stress (200 mmol·L^-1 NaCl) and B. cinerea. infection (by mycelium and spore suspension respectively) and induced resistance by applying SA, BR and CaCl₂ respectively and two or three of them. We did the study by planting cucumber seedlings in greenhouse, adding biotic chemical matter by leaf-spraying and root injection. Research results were as follows:1. Application of proper concentration of SA, BR, CTS and Spd could increase activities of Superoxide dismutase (SOD), peroxidase (POD) and catalase(CAT), contents of dissociating praline (Pro) and soluble carbohydrate in cucumber leaves, and dry mass of seedlings while decrease malondialdehyde (MDA) content and electrolyte leakage, which could increase cucumber's anti-salt stress and alleviate salt damage to guarantee seedling growth under salt stress.2. As biotic chemical matter, SA, BR, CTS and Spd showed distinctive concentration effect in inducing anti-salt effect. There were the appropriate concentration: SA 100～150 mg·L^-1, BR 0.005～0.05 mg·L^-1, CTS 150²00 mg·L^-1, Spd 100～200 mg·L^-1. As far as anti-stress effect was concerned, BR showed the best effect, and CTS, Spd and SA from better to good, with maximum decrease...