Impacts Of 6-BA And GA₃ On Seed Germination And Seedling Growth Of Lettuce Under High Temperature Stress

In order to overcome seed dormancy and seedling growth inhibition of lettuce caused by high temperature in summer,the seeds of "Bo Li " and "Zi Ye " were induced with GA₃,6-BA and mixture?GA₃ and 6-BA?individually in 2.5,5,7.5,10,12.5,15 mg/L under high temperature stress.When initiation treated,the seed germination,MAD content,relative conductivity,soluble protein and soluble sugar content,activity of antioxidant enzymes,seedling growth,chlorophyll content,respiration intensity and expression level of Hsp70 were detected.Main contributions of this work are as follows:1.Germination rate,germination index and seed vigor were increased under high temperature after treatment for 7 days in comparison to those of control,which indicates that initiation treatments break seeds dormancy caused by high temperature stress and promote seeds germination.2.Under high temperature stress,initiation treatment increased contents of soluble protein and soluble sugar significantly,reduced significantly MAD content and relative conductivity of seeds and significantly increased activities of SOD,CAT,POD.3.Initiation treatment promoted index of cotyledon lengths,hypocotyl lengths,radicle lengths,fresh weight and dry weight,and significantly relieved seedling growth inhibition.4.Initiation treatment promoted chlorophyll content,respiration intensity and metabolism levels of lettuce seedlings.5.Initiation treatment increased content of m RNA of Hsp70 and promoted heat tolerance of lettuce seedlings.6.Optimum concentration of GA₃,6-BA and GA₃+6-BA was 7.5 mg/L,10 mg/L and 5 mg/L,respectively.The initiation effect of mixture of GA₃ and 6-BA was better than that of GA₃ or 6-BA,which indicates that the two hormones work coordinately in seed germination and seedling growth.