Effect Of Soil Drought On The Growth And Accumulation Of Secondary Metabolite Of Pinellia Ternata (Thunb.) Breit

The medical herb,Pinellia ternata?Thunb.Breit.?has a long medical history,its tubers are applied for medicine.In order to explore the effects of drought stress on the growth and component accumulation of Pinellia ternata,soil water content were divided into three treatment,which are suitable water?CK?,medium drought?MD?and serious drought?SD?.Measuring the growth index,antioxidative enzyme activity,photosynthetic parameters and chlorophyll fluorescence parameters,and activities of key enzymes in nitrogen metabolism,PAL enzyme activity and its relative expression and content of secondary metabolites is to explore the effects of drought stress on the growth and the physiological mechanism of secondary metabolite accumulation in Pinellia ternata.Besides,exploring repeated droughts and rehydration on antioxidant system,photosynthetic characteristics and components of Pinellia Ternata.The specific results are as follows:1.The leaves of Pinellia ternata had higher activities of antioxidant enzymes?SOD,POD,and CAT?under moderate drought stress,which could scavenge active oxygen and inhibit membrane damage.Under severe drought stress,the activity of antioxidant enzymes was the lowest,and the content of malondialdehyde increased,indicating that the membrane was seriously damaged.The general trend of leaf length,leaf width,and plant height of Pinellia ternata was CK>MD>SD,which was due to water shortage inhibits root growth of Pinellia ternata,reduces root absorption of nutrients and minerals,and indirectly affected aboveground parts.The Pinellia ternata showes"small plants with narrow leaves."When the soil moisture content is relatively high,the growth of Pinellia ternata need to be met,and the growth is good.2.With the decrease of soil moisture,chlorophyll content,leaf transpiration rate?T_r?and intercellular CO₂ concentration?C_i?,net photosynthetic rate?P_n?,chlorophyll fluorescence parameters qP,ETR and Y?II?in Pinellia ternata leaf gradually decreases.With the increase of drought stress,the leaf transpiration rate?T_r?and intercellular CO₂ concentration?C_i?of Pinellia ternata were reduced at the same time,and the net photosynthetic rate was decreased.This indicated that drought stress caused the net photosynthetic rate of Pinellia ternata leaves to decrease by closing the stomata.Under sufficient moisture,qP,ETR,and Y???are higher and the reducibility of receptor Q_A in the PSII response center of Pinellia ternata leaves are strengthened,increasing the degree of opening of the PSII reaction center,and increasing electron transport activity,showing higher ETR and Y???level.Besides,the lower NPQ,meaning less heat dissipation,ensure the effective use of light energy share,the higher Y???is conducive to the conversion efficiency of light energy,promoting carbon assimilation and organic accumulation.Under moderate drought stress,NPQ was the highest,indicating that the share of the light energy captured by the antenna pigment was used in photochemical reactions are reducing to avoid light damage.It was also a way of adapting Pinellia ternata to drought stress.Low chlorophyll content and light energy capture under severe drought stress.Less,and therefore NPQ shows lower;Therefore,in the process of cultivation of Pinellia ternata,the irrigation work will be smoothly carried out,which will help improve the photosynthesis and accumulation of dry matter in the leaves of of Pinellia ternata.3.The general trend of NR,GOGAT,GS,GOT and GPT activities in Pinellia ternata is MD>CK>SD.Through this study,under moderate drought conditions,the activities of NR,GOGAT,and GS in the leaves of Pinellia ternata is enhanced,which is conducive to the transformation of inorganic nitrogen and the assimilation of organic nitrogen,promoting the progress of nitrogen metabolism,and then the role of transamination is through the GOT and GPT to synthesize essential amino acids for secondary metabolism,and then catalyzed by PAL,accumulating more secondary metabolite premise substances,which is conducive to the increase of secondary metabolites of Pinellia ternata.4.The water content in the tubers of Pinellia ternata under three moisture conditions is less than 14%,the ash content is less than 4%,and the leachate content is greater than 9%,which conforms to the standards of the“People's Republic of China Pharmacopoeia”?2015 year-edition,Part 1?.The bark of the bark of Pinellia ternata has less than 5.0 mg/kg of Pb,less than 0.3 mg/kg of cadmium?Cd?,and less than 20.0 mg/kg of Cu,which conforms to the“Green Industry Standard for Foreign Trade and Economic Cooperation of Medicinal Plants and Preparations”.WM/T2-2004),but under the treatment of the control group,Pb,Cd,and Cu in the bark of Pinellia ternata have not met the standard.The contents of polysaccharides and total acids in Pinellia ternata were the highest under suitable water treatments and the contents of total alkaloids were the highest under moderate drought stress,while the contents of polysaccharides,total acids and total alkaloids were the lowest under severe drought stress.Considering comprehensively,during the planting process of Pinellia ternata,moderate drought will contribute to the accumulation of secondary metabolite in Pinellia ternata.Therefore,moderate drought during the harvest period is beneficial to the accumulation of secondary metabolite in Pinellia ternata,which will accelerate the commucation of secondary metabolite.In the process of planting Pinellia ternata,avoiding heavy drought and providing enough water supply.5.This study shows that after experiencing repeated droughts and rehydration,the anti-oxidant system in the leaves of Pinellia ternata gradually increased,while the malondialdehyde content decreasing and the photosynthesis ability gradually recovering,indicating that repeated droughts and rehydration enabled Pinellia ternata to possess the ability of self-protection to defense against drought stress and to adapt to changing water conditions,minimizing damage from drought stress.At the same time,drought rehydration also has a significant effect on the active ingredient in the tubers of Pinellia ternata,but the mechanism of its effects still needs further study.