Pathways of root uptake and membrane transport of Cd2+ in the zinc/cadmium hyperaccumulating plant Sedum plumbizincicola

Abstract

Uptake and membrane transport of cadmium (Cd) in roots of the hyperaccumulator Sedum plumbizincicola X.H. Guo et S.B. Zhou ex L.H. Wu was characterized by assessing the impact of various inhibitors and ion channel blockers on Cd accumulation as well as the real-time net Cd²⁺ flux at the roots with application of the scanning ion-selective electrode technique. The uncouplers 2,4-dinitrophenol and P-type adenosine triphosphatase inhibitor Na₃ VO₄ significantly limited Cd²⁺ uptake and transport kinetics in the root of S. plumbizincicola. These findings indicate that Cd is actively taken up into the roots. The Cd content in plant was significantly decreased with pretreatments of the Ca²⁺ channel blocker La³⁺ or Gd³⁺ and the K⁺ channel blocker tetraethylammonium, as well as in the presence of higher concentration of Ca²⁺ and K⁺ . These findings indicated that uptake of Cd²⁺ into the root of S. plumbizincicola proceeds through ion channels that are permeable to both Ca²⁺ and K⁺ as confirmed by the direct evidence of real-time net Cd²⁺ fluxes at the root surface in the treatments with ion channel inhibitors, as well as in the presence of elevated concentrations of Ca²⁺ and K⁺ . In addition, the results suggested a role for phytochelatin and protein synthesis in mediating Cd²⁺ uptake by S. plumbizincicola. These findings increase the understanding of Cd²⁺ uptake and membrane transport pathways in roots of the Zn/Cd hyperaccumulator S. plumbizincicola. Environ Toxicol Chem 2017;36:1038-1046. © 2016 SETAC.

Keywords: Cadmium; Hyperaccumulator; Ion-selective electrode technique; Sedum plumbizincicola.