Cadmium uptake and membrane transport in roots of hyperaccumulator Amaranthus hypochondriacus L.

Hyperaccumulator Amaranthus hypochondriacus L. has huge potential in the remediation of cadmium (Cd)-contaminated soils and is necessary to understand the mechanism of Cd uptake by the roots. In this study, the mechanism of Cd uptake into the root of A. hypochondriacus was investigated using the non-invasive micro-test technology (NMT) by analyzing the rate of Cd fluxes at different regions of the root tip; also we assessed the impact of different channel blockers and inhibitors on the Cd accumulation in the roots, the real-time Cd fluxes, and the distribution of Cd along the roots. The results showed that the Cd influx was greater near the root tip (within 100 μm of the tip). All the inhibitors, ion-channel blockers, and metal cations had different degrees of inhibition on the absorption of Cd in the roots of A. hypochondriacus. The net Cd flux in the roots was significantly decreased by the Ca channel blockers lanthanum chloride (LaCl) by up to 96% and verapamil by up to 93%; as for the K channel blocker tetraethylammonium (TEA), it also caused a 68%-reduction on the net Cd flux in the roots. Therefore, we infer that the uptake by A. hypochondriacus roots is mainly through the Ca channels. The Cd absorption mechanism appears to be related to the synthesis of plasma membrane P-type ATPase and phytochelatin (PC), which is reflected by the inhibition of Ca upon addition of inorganic metal cations. In conclusion, access of Cd ions into the roots of A. hypochondriacus is achieved through various ion channels, with the most important being the Ca channel. This study will further enhance the literature regarding Cd uptake and pathways of membrane transport in roots of Cd hyperaccumulators.