Study On Dormancy Characteristics And Germination Physiology Of Cephalotaxus Sinensis Seeds

As a Tertiary relict plant,Cephalotaxus sinensis is an endemic species to China and has a broad prospect of landscape application.But the seeds remain deeply dormant in natural condition,and they will not germinate until the next or third year after landing.The article takes the Cephalotaxus sinensis seeds as the research object to study the dormancy causes.In this research,effects of the dormancy breaking processes with cold stratification and different concentrations of GA3 treatment,in order to learn more about the changes of storage substance content,enzyme activity and endogenous hormone,then reveal the mechanism of seed germination.The main results were as follows:(1)Seed viability is more than 90%,indicating greater germination potential.But it didn't germinate after cultivated for 30 d,indicating that Cephalotaxus sinensis seeds remain deeply dormant.(2)There was no permeable barrier,not the cause of seed dormancy.There were germination inhibitions in all parts of seeds,and the order of inhibitory effect was: testa < endosperm(embryo).And it proved that the presence of endogenous inhibitor is also a key reason of seed dormancy.(3)As the cold stratification duration increased,storage substances content,such as starch,protein and crude fat,decreased significantly;Howere,amylase and lipase activity and soluble sugar and free amino acid content showed an increasing trend.The result indicated that starch and proteins were hydrolyzed,resulting in changes in soluble sugar and free amino acid to provide energy for seed germination.The decomposition transformation and ulilization of storage substance,such as starch,protein,may be the key breaking dormancy.(4)As the cold stratification duration increased,ABA content decreased significantly,GA and IAA content showed an increasing trend,and the content of ZR decreased first then increased significantly.It turned that the decrease of inhibiting substance and the increase of promoting substance were the keys to break dormancy and promote germination.Besides,the ratio of GA/ABA,IAA/ABA and ZR/ABA showed an increasing trend,indicating that the ratio of different endogenous hormone played an important role in seed dormancy breaking.Different endogenous hormones work together in the process of seed germination.(5)At the concentration of 0,200,400,600 mg/L,seed had reached a germination to 12.7%,29.2%,21.7%,and 18.4%,which showed that cold stratification could break seed dormancy effectively.The result showed that the treatment of 200mg·L-1 GA3 combined with cold stratification was the best way to break seed dormancy,and it could be used in practice.