Characteristics of cadmium uptake and membrane transport in roots of intact wheat (Triticum aestivum L.) seedlings.

Wheat is one of several cereals that is capable of accumulating higher amounts of Cd in plant tissues. It is important to understand the Cd2+ transport processes in roots that result in excess Cd accumulation. Traditional destructive technologies have limited capabilities in analyzing root samples due to methodological limitations, and sometimes may result in false conclusions. The mechanisms of Cd2+ uptake into the roots of wheat seedlings (Triticum aestivum L.) were investigated by assessing the impact of various inhibitors and channel blockers on Cd accumulation as well as the real-time net Cd2+ flux at roots with the non-destructive scanning ion-selective electrode technique. The P-type ATPase inhibitor Na3VO4 (500 μM) had little effect on Cd uptake (p < 0.05) and the kinetics of transport in the root of wheat, suggesting that Cd2+ uptake into wheat root cells is not directly dependent on H+ gradients. While, the uncoupler 2,4-dinitrophenol significantly limited Cd2+ uptake (p < 0.05) and transport kinetics in the root of wheat, suggesting the existence of metabolic mediation in the Cd2+ uptake process by wheat. The Cd content at the whole-plant level in wheat was significantly (p < 0.05) decreased upon pretreatment with the Ca2+ channel blockers La3+ or Gd3+ and Verapamil, but not in case of pretreatment with the K+ channel blocker tetraethylammonium (TEA). In addition, the inhibitors of the Ca2+ channel, as well as high concentrations of Ca2+, reduced the real-time net Cd2+ fluxes at the root surface in SIET experiments. These results indicate that Cd2+ moves across the plasma lemma of the wheat root via Ca2+ channels. In addition, our results suggested a role for protein synthesis in mediating Cd2+ uptake and transport by wheat.