Studies On Seed Dormancy Mechanism Of Celtis Julianae Schneid.seeds

We investigated the reasons in seed dormancy of Celtis julianae Schneid.seeds.the types of inhibitor ingredients in Celtis julianae Schneid.seeds were indentified by using systematic separation method and GC-MS.At the same time,the germination percentage,endogenous hormones and storage substances during the stratification process of Celtis julianae Schneid.seeds were determined,The dormancy mechanism of Celtis julianae Schneid.seeds was studied in detail.The main results are as follows:1.The dormancy of Celtis julianae Schneid.seeds is mainly caused by endogenous inhibitors.The seed coat hinders the permeability of water,The water absorption rate of fresh and mature Celtis julianae Schneid.seeds is 9.88%when water absorption is saturated,and the water absorption rate is 14.33%when the water absorption of acid etching seeds is saturated.The germination rate of isolated embryo was about 27.50%,which indicated that the seed embryo of fresh Celtis julianae Schneid.had dormancy characteristics,but those are not the main cause of dormancy.The bioassay tests showed:The extraction solutions of the seed coat and endosperm all inhibit the germination of the B.pekinensis seeds and growth of B.pekinensis seedlings,and the endogenous inhibitors is the main cause of seed dormancy.2.All extraction phases are gained in seed coat and endosperm by using systematical solvent separation method.The results of bioassay tests of each separation phase showed that:Different organic phase extracts from seed coat and endosperm of Celtis julianae Schneid.all inhibit the germination of the B.pekinensis seeds and growth of B.pekinensis seedlings,among which the treatment of B.pekinensis seeds with methanol phase extract was the highest inhibitory,and the germination rate of CK was 42.28%and height of CK was 55.10%,and the root length was only 7.10%of CK.The GC-MS analysis showed that the main endogenous inhibitors in Celtis julianae Schneid.seeds were palmitic acid,linoleic acid,2,6-Dimethoxyphenol,butylated hydroxytoluene,,oleamide and erucyl amide.Furthermore,the results showed that the IC₅₀ of root growth in B.pekinensis seeds for 2,6-Dimethoxyphenol,butylated hydroxytoluene and linoleic acid were 72.277 mg/L,50.466 mg/L and 915.799 mg/L seperately.Therefore,the2,6-Dimethoxyphenol and butylated hydroxytoluene showed extremely strong inhibitory activity.3.At 120 days of stratification,the seed germination of five stratification treatments were64.50%,73.50%,70.75%,77.25%and 79.00%respectively.It shows that the treatment of outdoor stratification is the most effective method to break the dormancy of Celtis julianae Schneid.seeds,and GA₃ and stratification treatment can effectively break the dormancy of Celtis julianae Schneid.seeds.4.The results of endogenous hormones determination in Celtis julianae Schneid.seeds during stratification duration showed that ABA content continued to decrease,GA₃ and ZR content continued to increase,IAA content rose first and then decreased slightly,which helped to break Celtis julianae Schneid.seeds dormancy,the ratio of GA/ABA,IAA/ABA and ZR/ABA all showed a gradual increase,The effect of each hormones in the process of breaking Celtis julianae Schneid.seed dormancy was indicated.5.In the process of stratification,the results of physiological determination in Celtis julianae Schneid.seed showed that the content of soluble protein,starch and crude fat decreased gradually,the content of soluble sugar decreased slightly first,then increased,and finally decreased slightly;the total amylase activity showed a gradual upward trend.It is indicated that soluble protein,starch and crude fat were hydrolyzed into small molecular substances such as soluble sugar,which provided energy for Celtis julianae Schneid.seed germination.With the increasing of total amylase activity,the decomposition of starch can accelerate which can provide energy for breaking seed dormancy.