Critical review of fluoride in tea plants (<i>Camellia sinensis</i>): absorption, transportation, tolerance mechanisms, and defluorination measures
Jie Yang, Chengshun Liu, Jianlong Li, Yunfeng Zhang, Chen Zhu, Dachuan Gu, Lanting Zeng
Abstract
Tea (<italic>Camellia sinensis</italic>) is an important beverage worldwide. Consumers may develop tea-drinking fluorosis after long-term consumption of tea. However, the mechanisms underlying the absorption, transport, and accumulation of fluoride in tea plants, the tolerance of tea plants to fluoride, and the factors influencing these phenomena are unclear. This makes it difficult to address the problem of excessive fluoride accumulation in tea at the source. This review presents the sources and types of fluoride absorbed by different tissues of tea plants, the pathways of intercellular and intertissue transport, and the factors affecting fluoride absorption and transport. The mechanisms of fluoride tolerance mediated by exogenous ions, metabolites, transport systems, and antioxidant systems in tea plants are summarized. Furthermore, since high fluoride levels negatively affect the tea plant growth and tea quality, effective defluorination measures are discussed. These include the screening for low-fluoride tea varieties, cultivation management measures, fluoride-reducing manufacturing techniques, and specific brewing methods. Finally, the comprehensive defluorination of tea plants by improving transporter systems and enriching secondary metabolites is discussed. This review describes the current state of knowledge on the absorption pathway and fate of fluoride in the soil–tea plant system, and suggests strategies to reduce tea-drinking fluorosis.