Cadmium uptake by different rice genotypes that produce white or dark grains

A pot experiment was conducted to investigate cadmium (Cd) uptake by different rice cultivars that produce white or dark grains. Four cultivars with white grains (hereafter, white rice) and five cultivars with dark colors (hereafter dark rice) were selected for this experiment. Three levels of soil Cd concentrations, background (0), 5 and 10 mg/kg, were used. After harvest, plant biomass, tissue concentrations of Cd, Ca, Fe, Cu and Zn were analyzed. The results showed that Cd concentrations are significantly different between different genotypes, but when comparing the Cd concentrations for the two groups, no significant difference was found. For other divalent cations, Ca concentrations in dark rice were higher than those in white ones (P < 0.001 for shoots, P = 0.037 for roots); Fe concentrations in dark rice were also higher than those in white ones (P = 0.001 either in shoot or root); Zn concentrations in shoot of dark rice were higher than those in white ones, but no significant difference in roots. The total molar concentrations of divalent cations in dark rice were also significantly higher than in white rice. The potential benefit of higher Ca and Fe concentrations in dark rice and similar Cd concentrations in both groups is also discussed in this paper.