Mitigating effect of exogenous tannic acid on the stress of pesticides in tea

Pesticides are important tools to manage diseases, insect pests and weeds. And they can also affect the oxidation system and nutritional quality of plants. Based on the natural properties and structural characteristics of tannin acid, the potential effects of foliar application of tannin acid on the antioxidant system and nutritional quality of tea under oxidative stress induced by pesticides were studied. Compared with the pesticide application alone, the addition of 10 mg/L tannic acid significantly increased tea superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) activity, in which the POD activity is 4.69 times and 3.13 times that of the control and pyraclostrobin treatment respectively. Compared with the application of imidacloprid, bifenthrin and pyraclostrobin alone, the APX activity is increased by 340.74%, 114.71% and 271.70%. In addition, tannin acid significantly increased the total antioxidant capacity of tea and the content of proline. Tannin acid reduced glutathione, tea polyphenols, the content of malondialdehyde and membrane lipid peroxidation products. Tannic acid also increases the content of vitamin C, soluble protein, caffeine and free amino acids in tea. In summary, exogenous tannin acid can activate antioxidant enzyme activity of tea leaf, affect the accumulation of antioxidant non-enzymatic substances, alleviate the oxidative damage caused by pesticide stress in tea, and improve the quality of tea ultimately.