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The chemical form and subcellular and molecular distribution of cadmium (Cd) in the roots and leaves was investigated in two rice genotypes: the low Cd-accumulating ‘‘Guangyuanzhan No. 3’, and the high Cd-accumulating ‘‘Zhenguiai.’’ Elevated Cd level in the medium caused a significant increase in Cd concentration in all parts of the roots and leaves. The soluble fractions in leaves and roots of ‘Zhenguiai’ contained a higher proportion of the Cd than those in ‘Guangyuanzhan No. 3’. Furthermore, ‘Zhenguiai’ had a higher proportion of de-ionized water and 80% ethanol-extractable Cd, which is the most mobile Cd among its various chemical forms. Following gel filtration of the soluble fraction of leaf and root extracts of both genotypes, a compound with a molecular weight of ∼3 kDa, probably comprising phytochelatins (PCs), was the major Cd-binding component. The Cd concentrations in the fractions from the roots of ‘Zhenguiai’ were noticeably higher than those of ‘Guangyuanzhan No. 3’, which possibly resulted in the latter cultivar having a lower Cd mobility in the roots and less Cd translocation from the roots to the aboveground parts. [ABSTRACT FROM PUBLISHER]