Study On The Mechanism Of Seed Physiological Dormancy In Fritillaria Yuminensis X.Z.Duan

Fritillaria yuminensis X.Z.D is the only medicinal and ornamental bulb with blue flowers in the genus Fritillaria of Liliaceae.It has a very high development and utilization prospects.Its seeds need to go through two stages of morphological and physiological after-ripening before they can germinate.In this study,F.yuminensis seeds which had finished morphological dormancy were used as experimental materials,and the physiological dormancy reasons,the optimal method to break physiology dormancy and the changes of endogenous substances in the physiological dormancy process were systematically studied.The causes of physiological dormancy of F.yuminensis seeds and the optimal method of releasing physiological dormancy were analyzed,and the endogenous and exogenous synergistic priming factors in physiological dormancy were analyzed.The main results are as follows:(1)The seeds of F.yuminensis which were released from morphological dormancy had strong viability and a lot of endogenous inhibitors.The water-soluble inhibitors had stronger hinder effect on germination than methanol-soluble inhibitors,and the existence of inhibitors throughout the various stages of seed life activities,which was the fundamental reason causing seed physiological dormancy.The seed morphological and physiological dormancy was released naturally by 120 days,40 days by physiological dormancy,which were released in 100 days by GA3 50 mg·L-1,and 20 days by physiological dormancy.Exogenous GA3 50 mg·L-1 could effectively increase seed germination rate for F.yuminensis seeds,advance the germination time and shorten the physiological dormancy period,but too high or too low exogenous GA3 treatment was not conducive to the release of physiological dormancy.(2)During the process of releasing physiological dormancy,the activity of water-soluble inhibitors in the endosperm decreased gradually;Relative water content and free water content increased,bound water content decreased,the metabolic ability of cells increased,the process of releasing dormancy of seeds accelerated;The content of crude fat and starch decreased,which might be decomposed by lipase and amylase into small molecular compounds for seed germination;The content of soluble protein and amino acid increased at first and then decreased,which accorded with the characteristics of the accumulation and consumption of nutrients in seeds,the consumption of nutrients had little relationship with physiological dormancy,and the degradation of storage substances was for the preparation of germination;The action time of the key enzyme activity is different,POD acts on the physiological dormancy stage,but CAT acts on the seed germination stage,SOD and amylase activity act on the whole physiological dormancy and germination stage;In the endogenous hormones,GA3 was the first to promote the seeds to break the physiological dormancy,and IAA began to start after 10 days,while ABA content decreased after the release of physiological dormancy.(3)Exogenous GA3 50 mg·L-1 could reduce the activity of endogenous inhibitors,accelerate the transformation and degradation of nutrients,enhance the catalytic activity of key enzymes,accelerate the accumulation and release of endogenous hormones,and make them play the greatest physiological role,thus speeding up the process of breaking phy siological dormancy and promoting seed germination.