Effects Of Priming On Seedling Growth And Antioxidant Characteristics Of Lettuce Under High Temperature Stress

With continuous improving of the current level of national vegetables production, protected cultivation has became an important component of vegetable production. But lettuce(Lactuca. sativa var. angustana Irish.) seed has an obvious phenomenon of thermodormancyand can not germinate. Methods to relieve dormancy were summarized in this paper. This method can be generally classified into physical, chemical and composite relieving. Drying after ripening, stratification, alternating temperature treatments and other physical methods, soaking in solution of hormone and other chemical matter all can relieve seed dormancy of some plants.Many studies have shown that seed priming can effectively improve the vitality and production characteristics of lots of vegetables and crops. There are a great quantity of seed priming ways, most of which need expensive materials, complicated steps. But studies about priming with vermiculite are a little, besides there is not any domestic study about pepper seed primed with vermiculite and priming treatment with vermiculite.Priming with vermiculite was the best on the effects of priming, by comparing with two priming technology. And then studies were carried on about the effects of germination characteristics, physiological and biochemistry characteristic under high temperature, and the changes of the vitality artificially of lettuce seeds.Seeds of tow lettuce cultivars'Tenaire Erbaipi'and'Bilvqing'were used as test materials, and the effects of priming treatment with vermiculite on their seed germination and seedlings' physiological characteristics were studied under different temperaturs. The results showed that after the priming treatment the seed germination rate and germination vigor and the fresh and dry weights of seedlings were significantly higher than those of control. The priming treatment also singnificantly improved the activities of superoxide dismutased (SOD), peroxidase (POD), and catalase (CAT) in the seedling leaves but decreased the malonaldehyde (MDA) content. Making the soluble protein and soluble sugar contents in the seedlings significantly higher than those of control at 28℃. There were various priming effects on different cultivars. It was concluded from the above results that lettuce seed has an obvious phenomenon of heat dormancy, and priming treatment with vermiculite could abate heat dormancy of the lettuce seed and significantly promote the seed germination.The seeds of'Tenaire Erbaipi'and'Bi 1v qing' were used as test materials, and the effects of priming treatment with vermiculite and hormone were studied on the seed germination under 28℃. The results showed that after priming treatment of the seed with vermiculite and osmotic priming with hormone the germination rate, germination energy, the fresh and dry weights of seedlings and the activities of protective were significantly higher than those of control. Different varieties led to differences caused effect, and the vermiculite with hormonehe was better than the only vermiculite. Lettuce seed has an obvious phenomenon of thermodormancy. The above results indicated that priming treatment with vermiculite could reduce thermodormancy of the lettuce seed, and the vermiculite treatment can significantly promote the seed germination, and the priming treatment with vermiculite and hormone could breaking thermodormancy of the lettuce seed.