The effect of Caoganlin on the main biochemical components of tea leaves
Tea tree is a perennial economic crop with leaves, widely planted in many countries around the world. Weeds can compete with tea trees for fertilizer, water, and growth space, affecting tea yield and quality. Glyphosate is a common systemic herbicide with high efficiency, low cost, and wide weed killing spectrum. In recent decades, it has been widely used in weed management in tea gardens. At present, some provinces in China, such as Fujian and Guizhou, have implemented local regulations to restrict the use of glyphosate in tea gardens. However, it is still difficult to avoid glyphosate pollution in tea gardens due to improper drug use during production.

Glyphosate has broad-spectrum properties. While killing weeds, it is also absorbed by crop roots and transported throughout the plant, affecting crop growth and metabolism. Its mechanism of action is to interfere with the metabolic pathway of plant shikimic acid, affecting the synthesis of aromatic amino acids and causing metabolic disorders in plants. Therefore, the process of glyphosate acting on plant shikimic acid metabolism will inevitably affect the quality of crops. Previous studies have shown that the application of glyphosate leads to a decrease in the yield of crops such as corn, potatoes, and citrus. Some scholars have also begun to pay attention to the effects of glyphosate on the growth and metabolism of tea trees. After applying the recommended dosage of glyphosate herbicide in the tea garden, there were no signs of phytotoxicity in the aboveground parts of the tea trees; Through hydroponic system research, it has been found that glyphosate is absorbed by the roots of tea plants and transported to the leaves, which is highly likely to be the main pathway for glyphosate residue in tea. The research team found through the application of glyphosate to young and adult tea trees in the early stage that the glyphosate sprayed onto the soil was absorbed by the roots of the tea trees and transported and enriched to the leaves through the stems. At present, the specific effects of glyphosate application on the main biochemical components of tea leaves, such as amino acids, catechins, and alkaloids, have not been reported.

This study observed the apparent phytotoxicity of tea leaves after glyphosate application, and quantitatively determined the pesticide residues (glyphosate and aminomethylphosphonic acid) and major biochemical components (catechins, alkaloids, and amino acids) in tea leaves before (0 day) and after (7 and 33 days) glyphosate application, in order to explore the apparent phytotoxicity of tea leaves after glyphosate application, the metabolism of glyphosate in tea leaves, and the specific impact of glyphosate application on the main biochemical components of tea leaves. The relevant experimental results can provide reference for the safety control of glyphosate in tea production quality.

 

Glyphosate remains in tea leaves for a long time, and there is a risk of excessive glyphosate residue and AMPA biotoxicity; Secondly, the application of glyphosate can indirectly prevent the synthesis of components such as theanine, theobromine, epicatechin gallate, and epigallocatechin gallate in tea leaves, and alter the total amount and composition of free radical acids, catechins, and alkaloids in tea leaves, ultimately affecting the quality of fresh leaves. In addition, 10 key compounds with significant differences before and after glyphosate application in tea trees were selected through multivariate statistical analysis. The variable VIP values were ranked from high to low as follows: theanine, caffeine, epigallocatechin gallate, glutamine, epigallocatechin gallate, epicatechin, arginine, aspartic acid, glutamic acid, and epigallocatechin gallate. Therefore, it is recommended to avoid using glyphosate herbicides as much as possible in tea production.