Molecular Mechanisms Underlying the Impacts of Available-Iron Levels on the Accumulation and Translocation of 6:2 Chlorinated Polyfluoroalkyl Ether Sulfonate in Soybean (<i>Glycine max</i> L. Merrill)

Soil available-iron (Fe) is crucial for various physiological properties and processes in plants, particularly those related to the accumulation and translocation of per- and polyfluoroalkyl substances (PFAS). However, the mechanisms underlying the impact of available-Fe levels on PFAS accumulation and translocation in plants remain unclear. In this study, we investigated the impacts of available-Fe levels on the accumulation of an emerging PFAS, 6:2 chlorinated polyfluoroalkyl ether sulfonate (6:2 Cl-PFESA), in soybean, a typical dicot, through hydroponic experiments. Interestingly, Fe deficiency significantly enhanced soybean root volume, surface area, root tip count, and lipid content, thus favoring 6:2 Cl-PFESA adsorption on the root epidermis. However, its absorption and translocation to aboveground tissues were markedly suppressed due to significantly reduced transpiration rate and soluble protein content induced by Fe deficiency. Conversely, although excessive available-Fe also inhibited transpiration, it notably increased root membrane permeability and soluble protein content in aboveground tissues, thus greatly facilitating the absorption and translocation of 6:2 Cl-PFESA within soybeans. These findings demonstrate that appropriate Fe application in agricultural soils is essential to promote the growth of dicot crops and mitigate the potential ecological risks associated with the accumulation of 6:2 Cl-PFESA in the aboveground tissues of soybeans.