Effect Of GA₃ On The Release Of Physiological Dormancy Of American Ginseng Seeds

American ginseng（Panax quinquefolium L.）seeds have the characteristics of deep dormancy and belong to morphophysiological dormancy.The release of dormancy requires two stages:morphological after-ripening promotes embryo growth to mature size,and physiological after-ripening breaks its endogenous dormancy.The long seed germination period is one of the main factors affecting the reproduction of American ginseng.Morphological after-ripening overcomes the exogenous dormancy caused by seed coat and endosperm,which is relatively easy,while physiological after-ripening is mainly caused by the physiological state of the seed.The mechanism of physiological after-ripening is relatively complicated,and the degree of completion is difficult to distinguish.It is possible to establish a suitable artificial regulation method by distinguishing the morphological dormancy and physiological dormancy of American ginseng seeds,and analyzing their physiological and biochemical mechanisms respectively.The addition of exogenous hormones changes the level of hormone signals in the swelling stage of seeds,which is of great significance to artificially control the germination of American ginseng seeds.In this study,200ppm GA₃ treatment was used to increase the germination rate of American ginseng seeds and observe the growth of embryos in the physiological after-ripening stage.Combined with the detection of other physiological indicators,the mechanism of GA₃ treatment on the physiological dormancy release of American ginseng seeds was analyzed.It was found that GA₃ could reduce the content of POD,SOD and G6PDH in seeds.Targeted metabonomics was used to study the phytohormone changes of American ginseng seeds during the physiological after-ripening period.A total of 12 of the 24 hormone-related compounds tested appeared in the physiological after-ripening.Gibberellin（Gibberellin,GAs）,Abscisic acid（ABAs）,Jasmonic acid（JAs）,Cytokinin（CKs）and Auxins（Auxin,AXs）had obvious changes.They worked together to participate in the regulation of the physiological after-ripening,among which GAs,JAs and CKs could promote the release of physiological dormancy,and ABA and IAA inhibited the release of physiological dormancy.Through the control of these types of hormones,the release of physiological dormancy could be promoted.Transcriptome sequencing was used to analyze the differentially expressed genes of GA₃treated seeds and control seeds at different stages,and a total of 99 genes related to the above-mentioned five types of hormone metabolism and signal transduction were screened.It was found that the expression of GAs,ABAs and CKs on synthetic and metabolic genes was consistent with the results of targeted metabolome.As the annotated AXs and JAs anabolic genes are limited,no conclusion can be drawn yet.Hormone signal transduction is involved in the release and germination process of the whole physiological dormancy of seeds.