Exogenous application of ethephon regulates flower abscission, shoot growth, and secondary metabolites in Camellia sinensis

Tea plant (Camellia sinensis (L.) O. Kuntze) consumes a large amount of nutrients and water during the flowering stage, which compromises the tea growth and yield. Ethylene is an important plant hormone that plays pivotal roles in regulating plant growth and flowering. but there are few studies on flowering and growth of tea plants regulated by this plant hormone. Here, we investigated the effects of exogenous ethephon application on the abscission of flowers and flower buds in tea plants. The results showed that application of ethephon induced the production of endogenous ethylene and the peak of ethylene production occurred three days post ethephon spraying on the tea plants. Ethephon treatment induced the abscission of tea flowers and flower buds, leading to reduced amount of flowers in the tea plantations. Ethylene receptors (ETRs) play critical roles in ethylene-mediated cellular responses, and we found that there was a certain correlation between the effect of ethephon on the flower abscission and the expression of several CsETRs, including CsETR3, CsETR4, CsETR5, and CsETR6. Ethephon also induced the high activities of superoxide dismutase, peroxidase, and catalase three days after treatment. In addition, ethephon obviously reduced the tea polyphenol content and enhanced the caffeine content in tea plants. Treatment with ethephon (3000 mg L–1) significantly increased tea shoot length and production in the tea plantations in the following early spring. Overall, ethephon, in a range of concentrations, could effectively suppress the tea plant blooming and improve tea yield and quality to a certain extent.