Effects Of Exogenous H₂O₂ Pretreatment On Cold Resistance And Drought Resistance Of Sedum Sarmentosum Bunge And Its Influence On The Yield And Quality Of Medicinal Materials

Sedum sarmentosum Bunge is a perennial herb of the sedum genus in the Crassulaceae family.It has the effect of removing dampness and jaundice,clearing away heat and toxin.It can be used for dampness and heat jaundice,adverse urination,carbuncle and sore.It can be used to treat hepatitis,sore throat,furuncle and carbuncle,damp heat jaundice,etc.S.sarmentosum contains flavonoids,triterpenoids,cyanosides and other components,which have high value in ornamental,environmental protection,medicine and food.H₂O₂is an important signal molecule,which induces plant resistance to various biotic and abiotic stresses by regulating aerobic metabolism and defense systems（such as enzymatic degradation system and non-enzymatic scavenging system）.However,there are few reports on the application of exogenous H₂O₂in the stress resistance of medicinal plants,and one of the ecological functions of many active components in medicinal plants is to deal with the oxidative stress caused by stress.Therefore,the application of exogenous H₂O₂in the production of medicinal plants can improve the stress resistance of medicinal plants,improve their medicinal quality,reduce the production loss,and achieve high yield and quality,which is of great significance for medicinal plants.In this study,pot experiment was conducted to study the effects of different exogenous H₂O₂pretreatment on the growth,physiological and biochemical characteristics,chemical composition accumulation and in vitro antioxidant capacity of S.sarmentosum under low temperature and drought conditions,so as to induce high yield and high quality of S.sarmentosum.It can provide the basis for the cultivation mode of quality.The main results and conclusions are as follows:（1）In order to explore the effects of exogenous H₂O₂pretreatment on the adversity resistance and the yield and quality of S.sarmentosum,we hope to provide a basis for the high-yield and high-quality cultivation model of S.sarmentosum induced by stress signal substances.After spraying different concentrations of H₂O₂(0、1、10、100 mmol·L^-1)on the leaves of the S.sarmentosum,it experiences natural low temperature,and the growth index,biomass,content of various flavonoids and various in vitro antioxidant capacity are measured at harvest.The results showed that under low temperature conditions,spraying H₂O₂significantly increased the maximum branch length,leaf layers,number of branches,biomass,content of various flavonoids,and in vitro antioxidant capacity.With the increase of the concentration of exogenous H₂O₂,the number of leaf layers,branches,number of new buds,biomass and POD enzyme activity of S.sarmentosum showed a downward trend,while SOD,CAT enzyme activity and MDA content showed an upward trend.The biomass of 1 mmol·L^-1H₂O₂and 10 mmol·L^-1H₂O₂treatments increased by 209.38%and 87.50%compared with control treatment,respectively.The content of total flavonoids,total phenolic acids,quercetin,kaempferol,and isorhamnetin were the highest when treated with10 mmol·L^-1H₂O₂,which was 16.67%～37.84%higher than the control,followed by treatment with 1 mmol·L^-1H₂O₂.DPPH and ABTS free radical scavenging ability were found the strongest in 1 mmol·L^-1H₂O₂treatment,while 10 mmol·L^-1H₂O₂treatment showed the strongest hydroxyl radical scavenging ability and anti-lipid peroxidation ability.The results show that H₂O₂pretreatment under low temperature conditions is beneficial to increase the yield and quality of S.sarmentosum;after comprehensive comparison of biomass and active ingredient content,1 or 10 mmol·L^-1H₂O₂pretreatment is beneficial to improve the cold resistance of S.sarmentosum,and high yield and good quality.（2）Four treatments included suitable water treatment,suitable water+1mmol·L^-1H₂O₂,drought treatment,drought+spraying 1mmol·L^-1H₂O₂.The growth index,biomass,chemical composition and antioxidant capacity in vitro were measured at harvest.The results showed that under drought condition,spraying 1mmol·L^-1H₂O₂could significantly increase the number of branches,fresh weight per plant,leaf water content,ascorbic acid content,POD,SOD,CAT enzyme activities,soluble protein content,soluble sugar content,total flavonoids content,and reduce MDA content.Under suitable water conditions,spraying 1mmol·L^-1H₂O₂could significantly increase the maximum branch length,branch number,ascorbic acid content,total starch content,total phenolic acid content and isorhamnetin content of S.sarmentosum.The content of quercetin and kaempferol was the highest under drought condition.The scavenging ability of DPPH,ABTS and hydroxyl free radical was the strongest in suitable water+1mmol·L^-1H₂O₂treatment,and the anti lipid peroxidation ability was the strongest in drought+1mmol·L^-1H₂O_2.In general,the yield and quality of S.sarmentosum could be improved by spraying 1mmol·L^-1H₂O₂under drought or suitable water conditions.