Transport and redistribution of selenium in the bean plant (Phaseolus vulgaris)

After incubation for 3 h with (⁷⁵Se) selenate, the selenium distribution in the bean plant (Phaseolus vulgaris L. cv. Contender) through a 29-day period showed an uneven distribution: roots and trifoliate leaves were richer in ⁷⁵Se than stem and primary leaves. The high selenium concentration of roots resulted from the retention of selenate by the root cells: at the end of the 29-day period about 60° of the radioactivity was always ethanol-soluble, and when analysed by paper chromatography, proved to be selenate. By contrast, much of the radioactivity of the leaves was ethanol-insoluble, ⁷⁵Se being quickly captured in metabolic processes which immobilize it. During plant development, a portion of the total selenium remains mobile and is continually mobilized to the younger organs which display a rapid growth rate. This delivery results from a progressive liberation of selenate retained by mature organs, especially the roots, and from turnover in older leaf tissues, especially the trifoliate leaves.