Testing of outstanding individuals of Thlaspi caerulescens for cadmium phytoextraction.

Thlaspi caerulescens is known to hyperaccumulate high quantities of Cd with Cd concentrations up to 3000 mg kg(-1) in some populations from south of France. However, within these populations, the Cd concentrations can vary widely from plant to plant in a way that appears to be not entirely due to variations in soil Cd. The aim of this work was to investigate the variability in the Cd uptake ability of individual plants within a population and among seedlings grown from seeds from a single plant. Ten populations of T. caerulescens plants were selected from four locations (V: Viviez; SF: Saint Félix-de-Pallières; LB: Le Bleymard; CMA: Col du Mas de l'Air) depending of the extent and soil homogeneity of the site. One population from CMA consisted of the progeny of a single maternal plant. Hundred plants of each population were grown for three months in the same homogeneous and lightly Cd-polluted soil (about 20 mg total Cd kg(-1) dry soil). Cadmium uptake behavior of the plants was monitored by labeling the soil with 109Cd. To allow partial plant destruction, radioanalysis was performed on the largest leaf of each plant as an indicator of the total Cd concentration in plant shoots. Results showed significant differences in biomass production and Cd uptake by T. caerulescens between sites and between populations within sites. We observed a wide intra-population variation in biomass, Cd concentration and total Cd uptake. For these properties, 1 to 5 percents of the plants in each population varied by more than a factor of two from the mean values. The mean Cd uptake by the single-plant population from CMA was more than 40% higher than for the population at large. T. caerulescens would respond to traditional selection methods, which would significantly improve the phytoextraction of Cd.