The accumulation and fractionation of Rare Earth Elements in hydroponically grown Phytolacca americana L

Background and Aims: The widespread use of Rare Earth Elements (REEs) has resulted in localized soil pollution. Phytolacca americana L. has potential for REE phyto-extraction, but the related mechanism is not clear. Methods: In this study, the uptake and fractionation of REEs, and the influence of REEs on biomass production was investigated in hydroponically grown plants. Furthermore, the effects of Ca²⁺ and Al³⁺ on REE uptake, and the role of organic acids in REE translocation were also examined. Results: Results showed that biomass and accumulation of REEs in P. americana were enhanced at low REE concentrations, but inhibited at higher concentrations in solution. Significant heavy REE (HREE) enrichment was observed during the stem-to-leaf transport, with a quotient of ∑LREE/∑HREE decreasing from 0.75 to 0.23. Ca²⁺ and Al³⁺ treatments diminished REE accumulation. The ∑LREE/∑HREE ratio decreased from 0.84 to 0.62 with increasing input of Ca²⁺, but increased from 0.83 to 0.92 with higher Al addition. Conclusions: LREEs appear to enter into the root of P. americana through Ca²⁺ ion channels, whereas HREEs may share pathways with Al³⁺. Finally, citrate plays an important role in the translocation of REEs in P. americana.