Calcium enhances cadmium tolerance and decreases cadmium accumulation in lettuce ( Lactuca sativa )

We aimed at characterizing mechanisms controlling cadmium accumulation in lettuce, which is a food crop showing one of the highest capacities to accumulate this toxic compound. In this study, plants from three lettuce varieties were grown for eight days on media supplemented or not with cadmium (15 µM CdCl 2) and containing different concentrations of calcium (0.5, 1, 2.5, 5 and 10 mM Ca(NO 3)2). Our results show that exposure to cadmium resulted in biomass reduction. The biomass reduction was particularly high at 0.5 mM calcium but supplementation of the medium with increasing calcium concentrations alleviated the toxic effect of cadmium on the growth and water status of lettuce plants. The three lettuce varieties displayed different abilities to accumulate cadmium. Interestingly, increasing the calcium concentration in the medium resulted in a strong decrease in cadmium contents. These results suggest that cadmium uptake in lettuce plants is negatively associated with the presence of calcium in the culture medium, maybe due to a competition between these two cations for binding and absorption sites in roots. In conclusion, the results suggest that fertilization with Ca 2+ appears to be a