Study On The Quality Formation Of American Ginseng During Its Phenological Development Process Induced By Environment Factors

American ginseng(Panax quinquefolius L.)is a plant of the genus Panax ginseng in Acanthopanax family.Ginsenosides is the main pharmacologically active ingredient of American ginseng.American ginseng is a medicinal plant with large market demand,the quality of American ginseng are decreased significantly because of the replant failure.Therefore,it is vital to hunt new regions for American ginseng cultivation.It was found that American ginseng phenological performance as well as quality characteristics varied from location to location,but the exogenous factors driving this process are still poorly understood,and the relationship between the phenological development and ginsenoside accumulation under the influence of environmental factors are poorly understood.This study conducted field and cabinet experiments to explore the relationship among temperature,photoperiod,phenological development and ginsenosides accumulation in American ginseng,and to disclose the relationship between phenological development and quality formation of American ginseng.Firstly,phenological observation and ginsenoside content determination were carried out on the 3-year-old American ginseng from different cultivation locations in China.The relationship among environmental factors,phenological development and ginsenosides accumulation in American ginseng was studied by Principal component analysis(PCA)and stepwise multiple linear regression(SMLR)analysis to reveal its main environmental impact factors.Then,a serious of temperature and photoperiod controlled growth cabinet experiments were conducted in intelligent artificial climate growth cabinets.The effects of temperature and photoperiod on phenological rhythm and ginsenosides accumulation of American ginseng were studied by phenological observation,biomass and ginsenosides accumulation determination.In the field experiments,the results indicated that American ginseng from different original locations showed different phenological rhythm and different ginsenosides accumulation.Especially,those from higher latitude locations(Wuchang as an example,44.55°N)presented delayed spring phenology and advanced autumn phenology,but higher ginsenosides contents along with higher gene expression levels of ginsenosides biosynthesis than those from lower latitude locations(Wendeng as an example,37.23°N).Data analysis indicated that the phenological rhythm of American ginseng is closely related to the seasonal change of environmental factors,especially winter chilling duration,spring warming and autumn day-length shortening.In the cabinet experiments,results further proved that temperature interacting with photoperiod play a decisive role in the phenological development and ginsenosides accumulation of American ginseng in the absence of water and nutrient limitation.Both field and cabinet experiments indicated that that sufficient winter cold exposure coupling to spring long day-length photoperiod are beneficial environmental factor to normal spring phenology development,it can promote the expression of ginsenoside synthesis gene(Pq SE、Pq DS、Pq D12H)and increase the ginsenoside content.The shortening autumn day-length coupling to autumn cooling are beneficial environmental factor to normal autumn phenology development of American ginseng,it can promote the dormant stage of American ginseng at the right time and ensure that it experiences enough low temperature in winter to form a virtuous cycle of life history.Results also indicated that insufficient cold exposure and unsuitable day-length photoperiod are detrimental factors to the whole phenological development,and not good for ginsenosides accumulation and the quality formation in American ginseng.In conclusion,this study reveals that the coordinated regulation of temperature and photoperiod plays a leading role in the phenological development of American ginseng,and is also a decisive environmental factor for the quality formation of American ginseng.This study can provide guidance for predicting suitable cultivation locations and improving planting technique for high-yield and good-quality of American ginseng.