Effects Of Humus On Growth And Physiological And Biochemical Characters Of Polygonatum Cyrtonema Under Drought Stress

Polygonatum cyrtonema is a traditional Chinese medicinal herb in China.Its production and processing into edible products have led to a sharp increase in market demand.The large-scale cultivation can increase the production of Polygonatum cyrtonema and meet market demand.In order to explore the effects of humus on the growth,physiology and biochemistry of Polygonatum cyrtonema under drought stress,pot experiments were conducted.The humus soil and the loess soil substrate were used as the culture media,and four water gradients were set up:normal water supply(soil moisture content 80～85%),mild drought(soil moisture content 60～65%),moderate drought(soil moisture content 40～45%),and severe drought(soil moisture content 20～25%),Measure the growth indicators of Polygonatum cyrtonema,physiological and biochemical characteristics of leaves and roots,photosynthetic parameters of leaves,and changes in chlorophyll fluorescence parameters.The main research findings are as follows:(1)Humus can promote the growth of Polygonatum cyrtonema.The plant height,ground diameter,leaf length,leaf width,total root length,root surface area,root diameter,and root volume of Polygonatum cyrtonema increased,of which the leaf length and leaf width increased significantly,by 35.26%and 41.57%,respectively;Drought stress can inhibit the growth of Polygonatum cyrtonema,and humus can reduce its inhibition.(2)Humus was beneficial to the accumulation of polygonatum polysaccharide content and total saponins content,which increased by 45.43%and 12.72%respectively;Under drought stress,the polysaccharide content of Polygonatum cyrtonema decreased,and the total saponin content increased,while the humus could maintain the high content of both.(3)Under drought stress,humus can relatively improve the relative water content,chlorophyll content,antioxidant enzyme(SOD,POD)activity,increase the content of osmoregulation substances(soluble sugar,soluble protein),reduce the degree of membrane lipid peroxidation(relative conductivity,MDA content),improve the stability of physiological and biochemical properties of Polygonatum cyrtonema leaves,and alleviate the damage caused by drought.(4)Under drought stress,humus can relatively improve root activity,root SOD and POD activity,increase soluble sugar content and soluble protein content in root,reduce relative conductivity and MDA content in root,improve the stability of physiological and biochemical properties of Polygonatum cyrtonema root system,and alleviate the damage caused by drought.(5)The diurnal variation of net photosynthetic rate of Polygonatum cyrtonema exhibits a "bimodal" pattern,exhibiting a "midday photosynthetic break" phenomenon;Under drought stress,humus relatively increased the net photosynthetic rate(Pn),intercellular CO2 concentration(Ci),transpiration rate(Tr),and stomatal conductance(Gs)of Polygonatum cyrtonema.(6)Under drought stress,the F0 and qN parameters of chlorophyll fluorescence in Polygonatum cyrtonema increased,while the Fm,Fv/Fm,Yield,and qP parameters gradually decreased;Humus can keep Fv/Fm and qP parameters at a high level.