Phosphate availability mediates a trade-off between fluoride accumulation and food safety in Camellia sinensis
Abstract
Fluoride (F) contamination in agricultural soils poses potential risks to tea quality. Tea plants ( Camellia sinensis ) are known F hyperaccumulators, however, the mechanism by which phosphate (Pi) modulates F accumulation in this crop remains unclear. This study investigated physiological and molecular responses of C. sinensis under combined F-Pi treatments. Low Pi (0.01 mM) enhanced physiological tolerance to F stress by improving root activity, stabilizing membrane potential, and promoting the root-to-shoot translocation of F, Pi, Al, Ca, Fe, and Mn, while leading to increased leaf F accumulation. Conversely, high Pi (1 mM) increased F accumulation in roots and suppressed growth. Tissue-specific expression of CsFEX , CsCLCe , and CsPHT was associated with ion homeostasis. Heterologous expression in E. coli confirmed that CsFEX overexpression under 0.5 mM Pi conditions decreased intracellular F content. Collectively, these findings reveal a Pi-mediated trade-off between growth promotion and food safety in a hydroponic system, offering mechanistic insights and a basis for balancing tea productivity with safety, pending validation under field conditions.