Fluoride absorption, transportation and tolerance mechanism in Camellia sinensis, and its bioavailability and health risk assessment: a systematic review

Abstract

Tea is the one of the most popular non-alcoholic caffeinated beverages in the world. Tea is produced from the tea plant (Camellia sinensis (L.) O. Kuntze), which is known to accumulate fluoride. This article systematically analyzes the literature concerning fluoride absorption, transportation and fluoride tolerance mechanisms in tea plants. Fluoride bioavailability and exposure levels in tea infusions are also reviewed. The circulation of fluoride within the tea plantation ecosystems is in a positive equilibrium, with greater amounts of fluoride introduced to tea orchards than removed. Water extractable fluoride and magnesium chloride (MgCl 2) extractable fluoride in plantation soil are the main sources of absorption by tea plant root via active transmembrane transport and anion channels. Most fluoride is readily transported through the xylem as F − /F-Al complexes to leaf cell walls and vacuole. The findings indicate that tea plants employ cell wall accumulation, vacuole compartmentalization, and F-Al complexes to co-detoxify fluoride and aluminum, a possible tolerance mechanism through which tea tolerates higher levels of fluoride than most plants. Furthermore, dietary and endogenous factors influence fluoride bioavailability and should be considered when exposure levels of fluoride in commercially available dried tea leaves are interpreted. The relevant current challenges and future perspectives are also discussed.

The role of plant growth promoting rhizobacteria in strengthening plant resistance to fluoride toxicity: a review

“…The majority of F is quickly transferred as F/F-Al complexes to the leaf cell walls and vacuole across the xylem. The results suggest that tea plants detoxify F and aluminum (Al) simultaneously through cell wall accumulation, vacuole compartmentalization, and F-Al complexes, which may be a mechanism of F tolerance that enables tea to withstand higher F concentrations than most plants (Peng et al, 2020;Luo et al, 2022).…”

Bioaccumulation of Fluoride in Plants and Its Microbially Assisted Remediation: A Review of Biological Processes and Technological Performance

“…From the study of Zhang et al [190], it was observed that anion blockers inhibited the uptake of F − ions in tea plants (Camellia sinensis), and it was suggested that anion channels might play an essential role in the absorption of F − ions for the tea plants. Tea plants tolerate higher fluoride levels than other plants [218]. It was found that most of the F − ions uptaken by the roots of tea plants were readily transported to the leaves through the xylem [190].…”

Functional and molecular characterization of fluoride exporter (FEX) from rice and its constitutive overexpression in Nicotiana benthamiana to promote fluoride tolerance

“…Fluorine is a major groundwater and soil pollutant detected across major rice cultivating nations, such as China, India, Pakistan, Bangladesh, Indonesia and Myanmar (Mukherjee and Singh 2020). Alarming level of groundwater fluoride pollution occurs due to unplanned mining of fluoride-rich minerals, such as cryolite, appatite, etc., climatic weathering and edaphic ion-exchange processes (Peng et al 2020). Susheela (1999) reported fluoride level to be as high as 48 mg L −1 in the groundwater across Indian states.…”