The Role Of PEG In The Regulation Of Thermal Dormancy Of Fraxinus Mandshurica Rupr. Seeds

Seed secondary dormancy is common in nature,but the physiological mechanism of seed secondary dormancy is still unclear.PEG infiltration treatment has significant effects on seed dormancy and germination.In this study,we studied the effect of PEG permeation treatment and seed soaking treatment on seed germination ability,seed respiration rate,cell wall degrading enzyme activity and endogenous GA3 and ABA content by using dormant Fraxinus mandshurica seed as material.The role of PEG in the regulation of the physiological mechanism of thermal dormancy.Research indicates:(1)PEG treatment had different effects on seed germination under different germination temperature conditions.At the suitable germination temperature(15?),the seed germination rate(45%,26.83%,26.83%)after treatment with PEG(5%,25%,50%)was higher than that of the control treatment(20.5%),ie PEG permeation treatment was not induce secondary dormancy in Fraxinus mandshurica seeds.At high temperature(25?),medium and high concentration(25%,50%)PEG short-term(3d)osmotic treatment or high concentration(50%)PEG medium and long time(7d,14d)osmotic treatment seed germination rate(36%,38.5%;48%,60%)was significantly higher than the control treatment,the medium-high concentration PEG short-time permeation treatment or the medium-long time permeation treatment in the high concentration PEG significantly inhibited the thermal dormancy of the.mandshurica seed.(2)When seeds were germinated by ABA and GA synthetic inhibitors at high temperature,PEG treatment increased the seed germination ability of paclobutrazol soaked seeds,and weakened the effect of paclobutrazol on seed germination,but the effect of fluridone on seed germination was not Significantly affected.When the same PEG osmotic adjustment(5%,25%,50%),the seed germination rate(11.79%,21.67%,29.52%)after paclobutrazol treatment was significantly lower than that of water soaking treatment(22.34%,31.64%,56.62%);PEG0 The germination rate(60.56%)and germination index(0.99)of fluridone after seed soaking treatment were significantly higher than the control treatment(15.03%,0.26).(3)When seeds were germinated by hormone soaking and PEG permeation treatment,PEG treatment could promote seed germination after hormone soaking to antagonize thermal dormancy induction,and GA4+7,GA4+7+ethephon and ethephon+6-BA soaking can effectively prevent the heat dormancy of.mandshurica seed,6-BA,ethephon,ethephon+6-BA soaking and GA4+7 soaking antagonism,6-BA soaking and ethephon soaking synergy.Among them,with the increase of PEG treatment concentration(5%,25%,50%),the seed germination ability was significantly increased after soaking seeds with various hormones,GA4+7,GA4+7+ethephon and ethephon+6-at PEGO.The seed germination rate of BA soaking treatment(82.5%,62.5%,60.9%)was significantly higher than that of the control treatment(6.13%),GA4+7+ethephon,GA4+7+6-BA,GA4+7+ethephon+6-The seed germination rate of BA seed soaking treatment(62.5%,7.21%,23.19%)was significantly lower than that of GA4+7 soaking,and the seed germination rate of Ethephon+6-BA seed soaking treatment(60.88%)was significantly higher than that of 6-BA soaking(21.98%).),Ethephon(9%)soaking treatment.(4)PEG osmotic treatment at high temperature eliminates the pause state of seed physiological activity and increases the activity of seed endosperm cell wall degrading enzyme by weakening the seed respiration rate,weakening the endosperm barrier to embryo invasion,and changing GA3 and ABA in embryo and endosperm.The content regulates the hormone effect.Among them,at the high temperature,the same soaking treatment,PEG permeation treatment can significantly change the seed respiration rate and cell wall degrading enzyme activity.After eliminating germination stress(7-14d),soaking treatment and PEG permeation treatment had no significant effect on seed respiration rate.GA4+7 soaking treatment could significantly increase seed cell wall degrading enzyme activity.Only when soaking seeds were just finished,the contents of GA3 and ABA in different seeds were different,but the contents of GA3 and ABA did not change regularly after high temperature permeation treatment.The seeds with GA3 and ABA content after PEG permeation treatment were less than those without PEG permeation treatment.Different degrees of change.In summary,PEG osmosis treatment can prevent the induction of thermal dormancy of F.mandshurica seed by affecting seed respiration rate and cell wall degrading enzyme activity,and regulating physiological mechanisms such as hormonal changes.