Cr(VI) and Pi Inhibited Each Other's Uptake and Translocation By Arsenic Hyperaccumulator Pteris Vittata L.

We investigated effects of chromate (CrVI) and phosphate (Pi) on Cr and P uptake and translocation by As-hyperaccumulator Pteris vittata (PV). The plants were exposed to 1) 0.05 mM Cr(VI) and 0, 0.05, 0.25 or 1.25 mM Pi or 2) 0.25 mM Pi and 0, 0.05, 0.25 or 1.25 mM Cr(VI) for 24 h in a hydroponic system. PV effectively accumulated Cr (2,919 mg/kg in roots at 0.05 mM Cr(VI)) and P (5,100 and 3,500 mg/kg in the fronds and roots at 0.25 mM Pi). However, when co-present, Cr(VI) and Pi acted as inhibitors, negatively impacting their accumulation in PV. Increasing Pi concentrations reduced Cr concentrations in the roots by 62-82%, whereas increasing Cr(VI) concentrations reduced P concentrations in the fronds by 52-59% but increased P concentrations in the roots by 11-15%. Chromate apparently reduced phosphate transport and the proportion of P accumulated in fronds of PV. It may in part be due to competition between Pi and Cr(VI) during transport. Though Cr(VI) was supplied, 64-78% and 92% Cr(III) were in the fronds and roots, respectively. Using X-ray diffraction, Cr₂O₃ was detected in the roots confirming reduction of Cr(VI) to Cr(III) by PV. In short, Cr(VI) and Pi inhibited each other in uptake and translocation by PV and Cr(VI) reduction to Cr(III) in PV roots could be one of its detoxification mechanisms. The finding will help to understand the interaction of Pi and Cr during their uptake process in P. vittata.