Studies On Dormant Mechanism And Aging Character Of Liriodendron Tulipifera L Seed

The dormancy of forest tree seeds is a kind of eco-physiological property formed by plants to adapt the environment so that the species can live from one generation to the next generation and evolve normally. The dormancy is a good characteristic for plants' existing and developing, but is also inconvenient and difficult for seed germination. Therefore, the study on the property of seed dormancy and the methods of removing seed dormancy is one of the most important tasks in seed-research area.Seed dormancy and the way to overcome it, the water absorption character of seedcoat, the SOD and CAT activities, MDA content of liriodendron tulipifera L. were studied And GA3, IAA, ABA and ZR contents of seeds were measured in 2003 and 2004 at Nanjing Forestry University. The results were shown as follow:1.The seedcoat of liriodendron tulipifera L. has an excellent character of water absorption. So it may be not the main reason of seed dormancy.2.The outer coat of liriodendron tulipifera L. seed contains some germination inhibitors which have no significant effect on seed germination. So it also may not be the main reason of seed dormancy. But the inhibitors have significant effects on seedling height and root growth of Brassica Pekinensis.3.During the process of low temperature stratification, ABA content decline rapidly; GA3 content and IAA content rise; ZR content is just a trace in the seed and has no special changing pattern. IAA/ABA , GA3/ABA and ZR/ABA ratio rise rapidly.4.During the process of naked stratification at low temperature, hormone contents have a complex changing trend, but IAA/ABA, GA3/ABA and ZR/ABA ratio rise rapidly.5.The inhibitor, which is in the seed such as ABA, may be the main substance which causes seed dormancy. Dormancy breaking not only depends on the content of some kinds of hormone but also on the equilibrium of GA3, IAA, ZR and ABA.6.The treatment with GA3 can improve the seed germination, but it can not break seed dormancy completely.7.The 180d low temperature stratification treatment and 120d naked stratification treatment are he best way to break seed dormancy. The germination percentages of Liriodendron tulipifera L. seed with above two kinds of treatments are 88% and 90% respectively.8.SOD and CAT activitives of seed increase while MDA content and Electricalconductivity decrease at the beginning of aging (from 1d to 5d), but vice versa at the late aging period (from 5d to 20d).