Study On The Alleviation Effect Of Exogenous Tannic Acid On The Stress Of Three Pesticides Including Imidacloprid In Tea

The application of chemical pesticides is still the main means to control diseases,pests and weeds at current stage,but the threat of pesticides to environment,environmental organisms and non-target plants cannot be ignored.The application of pesticides will ultimately affect the yield and quality of agricultural products by interfering with the physiology,biochemistry,growth and secondary metabolism of plants.Tannic acid,as an important polyphenolic substance,have antioxidant properties due to its numerous phenolic hydroxyl groups,which was renewable,environmentally friendly and safe.In this study,imidacloprid,bifenthrin and pyraclostrobin were used as representative pesticides to study the effect of exogenous tannin acid alleviating pesticide stress by tea physiology and biochemistry,secondary metabolism,nutritional quality and pesticide residue behavior in tea.The main findings of the study are as follows:1.The effects of different concentrations of imidacloprid,bifenthrin and pyraclostrobin on tea seedlings were evaluated by biomass,photosynthetic pigment content,free radical scavenging rate and total antioxidant capacity of DPPH.The concentrations of imidacloprid,bifenthrin and pyrazole caused plant stress were 50 mg/L,50 mg/L and 200 mg/L,respectively.After the three pesticides were applied,the content of photosynthetic pigments in tea decreased significantly,and there was no significant difference in the activities of SOD,POD and CAT,and the activity of APX decreased significantly,and the content of MDA increased,and the content of tea polyphenols decreased significantly,and vitamin C,caffeine,soluble sugar and tea extract content were slightly increased,and metabolic was disordered in tea.2.The content of photosynthetic pigments in tea leaves with the addition of 10 mg/L TA was significantly increased by 15.72%,8.57% and 10.13%,respectively,compared with the single application of imidacloprid,bifenthrin and pyraclostrobin,which enhanced the photosynthesis of tea leaves.The activities of four antioxidant enzymes（SOD,POD,CAT and APX）in tea leaves were significantly increased after adding TA（10 mg/L）,among which the activities of SOD,POD,CAT and APX increased by 19.76%,87.03%,161.67% and 343.50%.After adding10 mg/L TA,the MDA content decreased by 13.44%,11.85% and 28.06%,respectively,compared with the single application of imidacloprid,bifenthrin and pyraclostrobin.The content of PRO,tea polyphenols and total antioxidant capacity of DPPH was significantly higher than those of single pesticide treatments,so TA alleviated the oxidative damage of pesticides.3.After application of imidacloprid,bifenthrin and pyraclostrobin,appling 10 mg/L TA could significantly improve the content and quality of vitamin C,amino acids,caffeine,soluble protein,soluble sugar and water extract in tea leaves.4.Non-target metabolomic analysis of tea treated with TA under stress caused by imidacloprid by UHPLC-MS.A total of 151 differential metabolites were detected,and 92 and90 differential metabolites were screened in two comparison groups（IMI vs CK,IMI-TA vs IMI）,respectively.Using KEGG enrichment analysis,it was found that there are 10 metabolic pathways enriched in both comparison groups,mainly polyphenol metabolism（flavonoid biosynthesis）,glutathione metabolism,amino acid metabolism and aromatic substance metabolism.A total of 14 metabolites were identified in the two comparison groups for polyphenol metabolism,9 amino acids and alkaloids were identified,and 4 aromatic substances were identified.The metabolite content abnormally increased or decreased under imidacloprid stress,and the addition of 10 mg/L TA brought it back to normal level,which promoted the metabolic balance and homeostasis in tea.5.A method for the detection and analysis of imidacloprid,bifenthrin and pyraclostrobin residues in tea was established by UPLC-MS/MS.The addition of 10 mg/L TA accelerated the digestion rates of the three pesticides in tea,and the half-lives of the three pesticides in tea were decreased by 27.40%,36.88% and 14.23%,respectively.In conclusion,imidacloprid,bifenthrin and pyraclostrobin as abiotic stresses seriously affected the growth,quality and safety of tea,induced the production of reactive oxygen species,membrane lipid peroxidation,and abnormal plant metabolism.The application of exogenous TA can promote the growth of tea seedlings,and enhance the activity of antioxidant enzymes and increase the content of non-enzymatic substances,and improve the nutrients and quality of tea,and accelerate the degradation and metabolism of pesticides in tea,and restore the metabolic balance of tea by affecting the metabolic pathway of flavonoids.Increase the content of catechins to improve the antioxidant capacity of tea.