Abstract: [Objective] The study was to reveal the seed dormancy mechanism of Acer yangjuechi and to obtain the effective dormancy-releasing method of improving seed germination, so as to improve the breeding efficiency, expand population size to mitigate the situation of being extremely endangered.[Method] Seed development of two different individuals growing in National Nature Reserve of Tianmu Mountain, Zhejiang province, was tested in 3 successive years. Through cabbage seeds germination test, the germination inhabitation of testa, endotesta and embryo was conducted. The techniques for seed dormancy releasing were studied by treatment of hormone-presoaking or stratification of testa-removed seeds at 5℃.[Result] Embryo of Acer yangjuechi was poorly developed and differs between the two individuals. The average percentage of well-developed seeds ranged from 9.73% to 33.98% and the average rate of viable seeds was 52.22%. Compared with other Acer plants, the lower percentage of well-developed seeds confirmed its high infertility rate. The methanol extractant from testa and embryo had the higher inhabitation effect on germination than that from endotesta which have a high correlation with the content of endogenous ABA. The content of endogenous ABA in embryo was the highest one, reaching 1 818.58 ng·g^-1, followed by those in testa with a value of 1 053.34 ng·g^-1 and endotesta with a value of 859.05 ng·g^-1. The complete seeds moist-stored at 5℃ and testa-removed seeds at room temperature can not germinate while the testa-removed seeds germinated and the germination rate increased significantly to 30%. And the treatment of presoaking seeds with 100 mg·L^-1 GA₃ or 200 mg·L^-1 6-BA for 12 hours promoted seed germination rate reaching to 46.67% and 43.33% respectively. The duration of seeds-presoaking with hormone had a significant influence on germination rate of seeds(P < 0.01)while hormone type and concentration didn't present significant influence(P > 0.05).[Conclusion] Seeds of Acer yangjuechi often has a high rate of infertility and become empty seeds, this is associated with limitation pollen supply. Outcrossing as a supplement to self-pollination favors pollination success and embryo development. Stands of the species should be planted in small tree-tree distance to promote outcrossing which leads to successful reproduction. Both forced dormancy by testa and embryo dormancy are existing in the seeds of A. yangjuechi. The main inhibitor of seed-germination is the endogenous ABA. Low temperature sand stratification of testa-removed seeds combined with hormone-presoaking could improve germination rate. It is recommended as the method for seed dormancy-releasing. The study is of significant implication to population enlargement and sustainable conservation of Acer yangjuechi.

Key words: Acer yangjuechi, embryo development, seed dormancy, seed germination, dormancy releasing