Regulation Mechanism Of Thermodonnancy In Fraxinus Mandshurica Rupr.Seeds

The secondary dormancy of seeds exists widely in natural conditions,it brings many problems to agriculture and forestry production,it will make our plants can not reach the expected effect of germination,thereby reducing yield and quality.At present,it is known that the factors such as high temperature,low oxygen and low water potential can induce secondary dormancy.However,the physiological mechanism is not clear.Fraxinus mandshurica seeds belong to the endosperm type seeds and have the phenomenon of thermodormancy.In this study,we use Fraxinus mandshurica seeds as materials and concern about this phenomenon that induction of thermodormancy of Fraxinus mandshurica seeds is closely related to the existence of endosperm environment.We study the physiological state and relationship between embryo and endosperm in thermodormancy,study the changes of activity of degrading enzyme of cell walls,study the hormone regulation of Fraxinus mandshurica seeds.By studying on the physiological regulation mechanism of thermodormancy,we hope to understand the characteristics of seed thermodormancy and enrich the theory about regulation mechanism of secondary dormancy,to provide the scientific guidance to agriculture and forestry production.The main results were as follows:(1)The endosperm is an important factor leading to the bad germination performance of thermodormant Fraxinus mandshurica seeds.The results showed that the effect of the change of endosperm state was significant,but the effect of the change of the embryo state was not significant.(2)There is a relationship between the bad germination performance of thermodormant Fraxinus mandshurica seeds and the decline of the activity of cellulase and hemicellulase of endosperm.The activity of cellulase and hemicellulase of endosperm decreased significantly with the increase of high temperature induced time.The activity of cellulase and hemicellulase had the largest decline under high temperature between 5 days and 10 days.The activity of cellulase and hemicellulase showed no significant difference in radicle part and cotyledon part.(3)The inhibitor of ABA synthesis(fluridone)can effectively reduce the degree of thermodormancy of Fraxinus mandshurica seeds and the inhibitor of GA synthesis(paclobutrazol)can increase the degree of thermodormancy of Fraxinus mandshurica seeds.During the process of causing the thermodormancy,the sensitivity of ABA of embryo increased significantly and the changes of sensitivity of GA of embryo were not significant with the increase of high temperature induced time.The regulation of ABA and GA3 is the important factor leading thermodormancy under high temperature.Both ABA and GA content decreased significantly by either of the two inhibitor treatment,so there is little influence on GA3/ABA by the treatment.