Transport of Selenate and Selenite into Astragalus Roots

After incubation for 1 hr with (75)Se-selenate, excised roots of Astragalus crotalariae, a selenium-accumulating species, and A. lentiginosus, a nonaccumulator, had absorbed radioactivity to levels well over the external concentration. About 98% of the radioactivity was ethanol-soluble, and when analyzed by column and paper chromatography and by electrophoresis proved to be selenate. This and previous evidence shows an active transport for selenate. Considerably less radioactivity was absorbed when (75)Se-selenite was supplied to the excised roots, and levels of the ethanol-soluble radioactivity did not exceed the external concentration. A good deal of the radioactivity was ethanol-insoluble. Analysis of the soluble radioactivity from both species showed appreciable conversion of selenite to other forms.