In many wild species, seeds are dormancy at maturity and will not germinate even under favorable environment conditions. Dormancy is a complex trail that is determined by many factors. Some studies have shown that cold stratification and the application of gibberellic acid (GA) can break seed dormancy and promote seed germination. The present study investigated the causes of plant dormancy and the effect of cold stratification and different concentrations of exogenous GA 3 in regulating Cephalotaxus sinensis seed germination. Results showed that C. Sinensis seeds have good water permeability, which suggested that seed coats were not the main cause that inhibited the seed germination. There were germination inhibitions in all parts of seeds, and the order of inhibitory effect was: testa < endosperm (embryo), which indicated that existence of germination inhibitions was the main reason causing seed dormancy. Endogenous GAs and IAA (indole-3-acetic acid) content increased, while ABA (abscisic acid) content decreased over the experiments. ZR (zeatin riboside) content decreased in the early phase of cold stratification, but rebounded by the end of the experimental period. The changes of endogenous hormone indicated that GA, IAA and ZR played a positive role in seed germination, whereas ABA was associated with seed dormancy. Besides, the relative ratio of GA/ABA, IAA/ABA and ZR/ABA may play a more important role than their absolute level during the seed development.

Cephalotaxus sinensis seeds can't germinate even in the appropriate environment. However, numerous studies have showed that cold stratification and gibberellin acid (GA) can break the seed dormancy and promote seed germination effectively. To investigate the effect of cold stratification and different concentrations of exogenous GA 3 on dormancy breaking in seeds of Cephalotaxus sinensis, we monitored germination rates and changes in soluble sugar, starch, amylase, soluble protein, free amino acid during cold stratification. The results showed that seeds stratified for 5 months germinated to 12.7%, while those disposed with 200, 400, 600 mg/L of GA 3 germinated to 29.2%, 21.7%, and 18.4%, respectively. Free amino acid content was enhanced significantly, whereas soluble sugar content decreased during 45 days and then increased constantly. Additionally, the main reserves such as starch, protein decreased significantly during cold stratification, and cold stratification induced increases in the activities of α-amylase, (α + β)-amylase. The preliminary results show that the combination of GA 3 and cold stratification has better effect to break seed dormancy.