Department of Plant Sciences

Cadmium contamination of the food chain is of serious concern. The uptake of this trace metallic element by plants is still poorly understood. Studies have generally focused on characterizing cadmium root absorption through short-term kinetic experiments, in presence or absence of some environmental factors. However, the kinetic parameters are most frequently measured on plants which were not exposed to the contaminant during cultivation. While regulation processes are evoked in the literature, there has been until now, no information about a possible feedback effect of chronic Cd exposure on the short-term root Cd uptake.

The aim of this study was to know if long-term pre-exposure to Cd during growth could trigger some regulation mechanisms for Cd uptake, at cell wall or at membrane levels. Two plants with contrasting Cd demands were investigated: maize and a Cd hyperaccumulating ecotype of alpine pennycress. A fractionation of root Cd allowed a separate assessment of apoplastic adsorption and of intracellular absorption.

After growth in solutions of low concentration (0.1 µM Cd), no significant regulation of root uptake was observed, for both apoplastic and symplastic compartments. On the other hand, both species reacted in similar ways to high Cd exposure (10 µM Cd) during cultivation: symplastic absorption was reduced while apoplastic adsorption was enhanced, in the same order of magnitude for the two contrasting plants.