Effects Of Artificial Aging On Endogenous Hormones,Starch Metabolism And Malt Quality Of Barley Seeds In Germination

Object: Aging can cause abnormal metabolism of seed and loss of seed vigor,which lead to detrimental effects on seed germination and seedling growth,as well as the plant growth,yield and quality.The objectives of this study were to reveal the effects of artificial aging treatment on seed vigor,endogenous hormones,starch metabolism of barley seed in early germination and its malt quality,thus making aging mechanism more perfect and providing theoretical basis for storage of germplasm and selection of high quality raw materials in beer production.Methods: In this study,artificial aging method with conditions of high temperature and high humidity(40 ℃,80 % RH)was adopted to simulate natural aging process of barley seeds(Ganpi4,Kenpi 7,P12-8 and 9810).Normal(unaged)seed as control.Indicators were determined including seeds vigor,endogenous hormones,starch granules,starch content and amylase activity of barley seed in early germination(0~72 h).Results:(1)Standard germination tests of barley seeds were done,then germination indexes were measured at the same time.The results showed that aging reduced germination potential,germination rate,germination index and vigor index of barley seeds.And it decreased significantly after 9 d aging.Besides,the method of TTC staining was used to determine embryo activity of barley seed with different vigor.The results indicated that TTC reduction intensity decreased gradually with the increasing of aging time.Combining the germination characteristics and embryo vigor,the order of resistance to aging in different varieties was 9810>Ganpi4>P12-8>Kenpi7.(2)The changes of endogenous hormone contents were detected by ELISA in the endosperm of barley seeds with different vigor levels.The results showed that contents of endogenous GA3,IAA,ZR,ABA,BR and Me JA had substantially change in the endosperm of aging barley seeds.Contents of GA3,BR and ZR were lower than those of the control,but contents of IAA and Me JA were higher than those of the control at the seed absorption stage.Then the contents of GA3,BR and ZR were higher than those of the control,but the contents of IAA and Me JA were lower than those of the control with the extension of seed germination.However,content of ABA was higher than that of the control at all germination process.(3)We observed morphological characteristics and apparent characteristics of starch grains of seeds barley with different vigor levels at 72 h germination.The results showed that aging had no effect on morphological characteristics of starch granule of barley endosperm.But it increased the small starch granules and reduced large starch granules of endosperm.In addition,the equatorial grooves and pin holes decreased significantly at the surfaces of the large starch granules at the germination 72 h.(4)Barley seeds with different vigor levels were treated with germination so as to determine its content of starch.The results showed that reduction of contents of amylopectin and amylose delayed gradually with increasing of aging time.There were significant differences between the aging 15 d and control in amylopectin and amylose contents of all barley.Furthermore,the correlation between the content of starch and the germination indexes of seeds were analyzed.The results showed that the contents of amylopectin and amylose were respectively significant negative in correlation with the germination germination indexes of seed within certain range.(5)Barley seeds with different vigor levels were treated with germination in order to determine its amylase activity.The results showed that activity of α-amylase,β-amylase and limit dextrin decreased gradually with increasing of aging time.There were significant differences between the aging 15 d and control in amylase activity of all barley.Furthermore,the correlation between the activity of amylase and malt quality properties of seeds was analyzed.The results showed that the activity of α-amylase,β-amylase and limit dextrin were respectively significant positive in correlation with α-amino nitrogen,anhydrous extract,folbaeh and saccharogenic power,but respectively significant negative in correlation with viscosity within certain range.Conclusion: Aging treatment could break the balances between GA3,IAA,ZR,ABA,BR and Me JA,which let to the activity of α-amylase and β-amylase and limit dextrin enzyme,then the degradation of starch were delayed,finally the decline of seed vigor and malt quality of barley.