Environmental Context. Phytoremediation, the process of using plants to remove metals from contaminated soils, shows promise as a low-technology method for economically removing arsenic, and other toxic metals, from soil. Arsenic transport studies in vascular plants have examined how arsenic is taken up, chemically modified, and transported from roots to other parts of the plant. No studies, to our knowledge, have examined the effect of low-level doses of arsenic on the roots themselves. This paper shows, for the first time, that arsenic at low levels may beneficially affect root development.

Abstract. Corn (Zea mays) roots were grown in culture on modified Strullu–Roman medium in two separate experiments. Roots were exposed to one of four treatments combining arsenic (100 µg L^-1 or 0.0 µg L^-1) and phosphorous (4.8 mg L^-1 or 0.0 mg L^-1). The cultures were allowed to grow for 18 days or 21 days before they were used for quantitative measurement of root mass, root length, number of branches, and branch length. Results indicate roots grown in medium lacking phosphate but containing arsenic were longer and had greater mass than roots grown in medium with only phosphate. The data presented here suggest that arsenic at low levels might be beneficial for root development.