| The study of the physiological mechanism in process of seed germination can help us to learn physiological and ecological identity of seed germination, and can guide yield in nursery. In the study, seed of Manchurican ash (Fraxinus mandshurica Rupr.)that breaked dormancy for material. We studied the the process of seed germination in different temperatures, and physiological and biochemical change in the process of breaked secondary dormancy. The results were as follow:Seed of breaked first dormancy germinated in different temperatures (ten levels). Change temperature for seed germination was better than constant temperature. 15℃/10℃was the optimal change temperature, and 10℃was the optimal constant temperature. Seeds were secondary dormant when constant temperature more than 20℃.The material conversion block in Fraxinus mandshurica seeds causes a principal reason which is the secondary dormancy under high temperature. When the temperature was 25℃that can induced secondary dormancy, contents of GA3, IAA, ZT decreased, content of ABA increased, the ratio of GA3 and ABA,IAA and ABA, ZT and ABA decreased. And activity of lipase andβ-amylase of seed were restrained, decomposition of fat and starchy slowed, metabolizes of dissoluble albumen and sugar were restrained in different level. We can know that the ratio of ZT and ABA with content of dissoluble albumen and starch were statistically different at the level of p＜0.01 and p＜0.05 respectively by analysis the change of every phyological index in process of seed germination in 25℃. Metabolize of cache were restrained in 25℃, which related to the ratios of several hormones decrease, which induced seeds to secondary dormancy.Soak secondary dormant seeds in six treatments of different concentrations and hormones. Ethephon of 10-3mol/L breaked dormancy effectively that induced by high temperature (25℃).Ethephon effect advance materail conversion in secondary dormancy seed and germination. Ethephon of 10-3mol/L increased endogenetic content of ZT and IAA, and decreased significantly content of ABA and GA, and increased significantly the radios of GA3 and ABA, IAA and ABA, ZT and ABA, and increased activity of lipase andβ-amylase of secondary dormancy seeds, and accelerated mobilistion of cache, and enhanced the ability of dissoluble sugar and albumen supply energy and nitrogen to immature embryo. The activity ofβ-amylase with content of starch were statistically different at the level of p＜0.05 negatively and with the ratio of GA and ABA were statistically different at the level of p＜0.05 positively by analysis the change of every phyological index in process of breaked secondary dormancy. The activity of lipase with the ratios of IAA and ABA, ZT and ABA were statistically different at the level of p＜0.05 positively. The stagnant metabolism of cache resumed in secondary seed by ethephon changed the ratio of positive hormones of GA3, IAA, ZT and negative hormones of ABA, which was the important reason of break secondary dormancy and promote germination.
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