Effects Of Water Stress On Growth Physiological Characteristics And Quality Formation Mechanism Of Panax Ginseng C.A.Meyer

Panax ginseng C.A.Meyer is a perennial herb.Soil is the material basis that affects the growth and quality of ginseng,among which soil moisture directly affects the soil structure and nutrient forms.The growth,ginsenosides synthesis and soil physical and chemical properties of ginseng plants could be affected by regulating soil water content.This paper choosed three-year-old ginseng seedlings as test materials,field experiment was carried out to study the effects of water stress on ginseng growth,quality and physiological characteristics and the influence of soil characteristics.Transcriptome sequencing was used to study the molecular mechanism of ginseng in response to water stress.The aim was to provide theoretical basis for soil water regulation for ginseng high quality planting.The main results are as follows:1.Study on the effects of long-term and short-term water stress on the growth of ginseng.It was found that long-term drought stress significantly inhibited the growth of the growth of ginseng plants,fruits,seeds and roots,and accelerated the wilting of ginseng plants.The higher the degree of drought stress was,the greater the inhibition effect was.The water logging stress made the ginseng root form short and thick,and some roots red skin.Drought stress significantly inhibited the growth of ginseng plants,fruits,seeds and roots in both green and red fruit stages.The earlier the drought stress treatment,the greater the inhibition effect was.Drought stress accelerated the wilting of ginseng plants at green fruit stage,red fruit stage,and post-fruit ginseng root growth stage,and the later the drought stress treatment,the greater the negative effect.2.Study on the effects of long-term and short-term water stress on ginseng quality.It was found that long-term severe drought stress was beneficial to the accumulation of monomer ginsenosides Rb₁,Rb₂,Rb₃,Rc,Rf,Rg₁ PPD（protopanaxadiol）ginsenoside,PPT（protopanaxatriol）ginsenoside and total ginsenosides.Drought stress at green fruit stage and red fruit stage and post-fruit ginseng root growth stage was beneficial to the accumulation of monomer ginsenosides Re and Rg₂,and the production of monomer ginsenosides Re and Rg₂ were increased under drought stress at post-fruit ginseng root growth stage.Waterlogging was beneficial not only to accumulation of monomer ginsenoside R₁,but also to increase the production of monomer ginsenoside R₁.3.Study on the effects of long-term and short-term water stress on physiological indexes of ginseng.It was found that long-term drought stress and short-term drought stress could increase the contents of MDA（Malondialdehyde）,soluble sugar,soluble protein and proline,and the activities of SOD（Superoxide dismutase）,POD（Peroxidase）and CAT（Catalase）in ginseng root.The contents of MDA,soluble sugar,soluble protein and proline increased with the prolongation of treatment time,while the activities of SOD,POD and CAT decreased first and then increased with the prolongation of treatment time.Drought stress increased the content of ABA（Abscisic acid）in ginseng root,while waterlogging stress significantly increased the content of JA（Jasmonic acid）.4.Transcriptome analysis of ginseng under water stress.It was found that many differentially expressed genes（DEGs）had been enriched to plant hormone signal transduction pathways.There were 12 DEGs in ABA signal transduction pathway responding to drought stress,6 DEGs responding to waterlogging stress,and 5 DEGs responding to both drought stress and waterlogging stress.These genes could be used as resistance genes for subsequent studies.A total of 28 genes of key enzymes for ginsenoside synthesis were identified in the ginsenoside synthesis pathway,among which 7 DEGs responded to drought stress,3 DEGs responded to waterlogging stress,and 1 DEG responded to both drought stress and waterlogging stress.These genes may play important roles in regulating ginsenoside accumulation under water stress.It can be used as a candidate gene in response to water stress for further study.5.Study on the effects of water stress on soil properties.It was found that drought stress significantly inhibited the activities of catalase,sucrase,urease and acid phosphatase in rhizosphere soil,and significantly enriched ammonium nitrogen in rhizosphere soil.Water logging increased soil bulk density,inhibited the activities of catalase,sucrase,urease and acid phosphatase in the rhizosphere soil,and enriched Fe and Mn in the rhizosphere soil.