Physiology Mechanism Of GA And Ethephon To Release Thermodormancy In Fraxinus Mandshurica Rupr. Seeds

Fraxinus mandshurica Rupr.is an important timber species in northeast of China,whose reproduction is mainly on seeds.Under high temperature,the seeds can get into the model of thremodormancy easily,which affects the growth of the seeds seriously.At present,it is known that GA4+7 and ethephon can release the thermodormancy of.mandshurica seeds effectively,but the physiological mechanism is still unclear.In this study,the seeds of.mandshurica,which in the model of thremodormancy,were used as materials.Treating the seeds with different plant growth regulators,then analyzing and comparing the effects of different treatments on seeds germination,pectinase activity,cellulase activity,endogenous hormone content,seeds respiration,during the thermodormancy released by GA4+7 and ethephon.To explore the difference and connection between GA4+7 and ethephon in the mechanism of thermal dormancy release of.mandshurica seeds.The results can enrich the theory of hormone regulation in secondary dormancy of seed,and thus more scientifically guide agricultural production practices.The main results were as follows:(1)Paclobutrazol inhibited GA4+7 and ethephon to release the thermodormancy of.mandshurica seeds,and the inhibitory effect of paclobutrazol on ethephon to release the thermodormancy was significantly higher than that of paclobutrazol on GA4+7 to release the thermodormancy.Exogenous 6-BA and ethephon could antagonize the effect of paclobutrazol inhibited GA4+7 to release the thermodormancy of F.mandshurica seeds.6-BA could antagonize the effect of paclobutrazol inhibited GA4+7 and Ethephon to release the thermodormancy of.mandshurica seeds.When GA4+7 released the thermodormancy of F.mandshurica seeds,100μmol/L paclobutrazol was added,and the seeds germination rate(73%)was significantly lower than that without paclobutrazol treatment(87%).When ethephon released the thermodormancy of F.mandshurica seeds,The germination rate of adding 1 μmol/L paclobutrazol(29.7%)was significantly lower than that without paclobutrazol(62%).When the concentration of paclobutrazol was the highest(100 μmol/L),the seeds germination rate was the lowest(11.88%).When paclobutrazol(100μmol/L)inhibited GA4+7 from releasing the thermodormancy of F.mandshurica seeds,the addition of 6-BA or ethephon could significantly increase the seeds germination rate.When GA4+7 and paclobutrazol are present at the same time,the addition of 6-BA or ethephon can significantly increase the seed germination rate.When both ethephon and paclobutrazol were present,the addition of 6-BA or ethephon can significantly increase the seed germination rate.When both ethephon and paclobutrazol were present,the addition of 6-BA could significantly increase the germination rate of seeds.The effect of adding ethephon on seed germination was not significant.(2)High concentration of fluridone(200 μmol/L)inhibited GA4+7 and ethephon to release the thermodormancy of.mandshurica seeds,6-BA promoted GA4+7 and ethephon released the thermodormancy of F.mandshurica seeds,ABA and the inhibitors of ethylene synthesis(AVG,AIB)had no significant effect on the release of thermodormancy of F,mandshurica seeds by GA4+7 and ethephon.When GA4+7 and ethephon released the thermodormancy of.mandshurica seeds,the germination rate of high concentration fluridone(200μmol/L)was 70.12%and 20.36%,respectively,which was significantly lower than that without fluridone treatment(87%,62%),the germination rate of seeds after adding 6-BA was 78%and 60%,respectively,which was significantly higher than that of untreated 6-BA(73%,41%),and the germination rate of seeds after adding ABA and ethylene synthesis inhibitor(AVQ AIB)was not significantly different from that of the untreated treatment.(3)GA4+7 and ethephon released the thermodormancy of F.mandshurica seeds,accompanied by an increase in cellulase activity of the endosperm(0~3d),enhanced seeds respiration rate,and increased GA3 content in the embryo(7~14d).(4)Paclobutrazol had different main action sites for seeds during the thermodormancy released by GA4+7 and ethephon.When ethephon released the thermodormancy of F.mandshurica,the cellulase activity of the endosperm was decreased and the GA3 content of the endosperm was decreased when the addition of paclobutrazol was compared with the addition of paclobutrazol.However,when GA4+7 released the thermodormancy of F.mandshurica,polypaxazole was added.Compared with paclobutrazol treatment,the GA3 content in the embryos decreased(10-14d),and there was no significant difference in the cellulase activity of the endosperm.This indicates that when ethephon released the thermodormancy of F.mandshurica,paclobutrazol can inhibit the cellulase activity of endosperm and inhibit the synthesis of GA3 in endosperm.However,when GA4+7 released the thermodormancy of F.mandshurica,paclobutrazol mainly affects the synthesis of GA3 in the embryo.