| The seeds of osmanthus americanus have much low germination percentage due to its dormancy phenomenon under natural condition. This research aims to determine the causes and mechanism of seed dormancy so that the methods to break seed dormancy can be found out. The results showed as follows:1. The germination percentage of osmanthus americanus's isolated embryo with light treatment is 100%, whereas that of intact seeds and removing seed-coat seeds are all only0%. The seeds without endosperm near embryonic root can germinate, when they have been cultured for 14days under the condition with constant temperature( 25℃) and light. While under the same condition, only can some exposed cotyledons of the seeds without endosperm near cotyledon grow green in 7days, but the embryonic root hasn't any elongation. It shows that the endosperm of osmanthus americanus is the main factor causing seed dormancy.2. There are irregular folds and obvious pores at outside surface of osmanthus americanus seed-coat as well as many mycropyles scared over the longitudinal bed profile of it. Therefore, the seed-coat is not the main factor for causing the seed dormancy.3. The results of transmission observation on osmanthus americanus seed indicate that endosperm cell's membrane has disintegrated, and at the later stage of stratification, the starch and fatty granule massively appears. All of these changes showed that the nutrients in the endosperm can decompose constantly to provide the material and energy for seed germination and growth during cold stratification.4. In this paper, the most effective method was removing seed shell + GA treatment + cold stratification for mixture of GA3 and sand. It can make germination rate reach 74% after 45day's treatment.
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