The Dynamics Of Endogenous Hormone Content In Seeds Of Halenia Elliptica And Their Effect On Seed Germination

The endogenous hormones have been highly concerned because they are important to adjust seed germination and dormancy.However,no theory or hypothesis on their dynamics with environment and mechanism to adjust seed germination has been widely accepted.In this study,seeds of Halenia elliptica which is widely spread in the northeast Qinghai-Tibet plateau were used to test the dynamics of endogenous hormones content and germination of seeds collected from different altitudes in different storage conditions,under different germination conditions and in the process of seed germination,to analyze the effects of environment conditions on endogenous hormones contents and relationships between seed germination and endogenous hormones contents.The results showed that:(1)In any storage conditions,seed germination of Halenia elliptica showed circulative fluctuation with storage time.Seeds collected from lower and medial altitude showed a germination peak every year,however,seeds collected from higher altitude showed annual cycle under room storage but germination peak moved three months to the left,and about biannually cycle under cold storage.Thus,seeds of Halenia elliptica might have dormancy cycle,and the difference in seed germination with altitude might be caused by adaptation to alpine envrionment.(2)Seeds germination of Halenia elliptica under room storage had higher percentage than those under cold storage;germination percentage in darkness was higher than those in light;there was significant difference in seed germination percentage among altitudes,those of seeds collected from medial altitude was highest and those of seeds from lower altitude was lowest.(3)The storage time had different effects on endogenous hormones contents of Halenia elliptica seeds collected from different altitudes under different storage conditions.As a whole,the endogenous hormones contents of Halenia elliptica seeds had larger variation under room storage.Under room storage,there were significant difference in each endogenous hormones contents of Halenia elliptica seeds collected from different altitudes;however,under cold storage,the effects of storage time on endogenous hormones contents were dependent on altitude.(4)Seed germination of Halenia elliptica was not controlled by the contents of promoters or inhibitors,and also had not obvious correlations with ratios of promoting substance to inhibitor.Seed germination was positively with the content of GAs and negatively with the content of IAA,IAA/ABA.But percent germination would be higher only when the content of CTK was higher.(5)From seed absorption to first germination,the endogenous hormones contents of Halenia elliptica seeds collected from different altitudes showed different dynamicsunder different germination conditions.In any case,the GAs content tended to get the same value,the CTK content increased gradually and the ABA content almost remained stable.Furthermore,the CTK content had a higher value if the ABA content had a larger value.Therefore,in this study,the relationships among endogenous hormones might be consistent with the "three-factor" hypothesis proposed by Khan,that is,CTK antagonized ABA,to relieve or eliminate the role of ABA and promote the role of GAs.