Manganese Hyperaccumulation in Phytolacca americana L. from the Southeastern United States

Most plants that hyperaccumulate metals are restricted to soils with elevated concentrations of those metals. Recent reports have suggested that some Phytolacca species in China can hyperaccumulate manganese (Mn). Phytolacca americana L. (Pokeweed) is a ubiquitous weed of roadsides and waste areas in its native range in the southeastern United States, and has no known association with high-Mn soils. We investigated whether Mn hyperaccumulation also occurs among such plants. Field-collected samples contained approximately 2000 mu g Mn g(-1) dry weight, whereas other species from the same site ranged from 50 to 450 mu g g(-1). Seedlings of P. americana were transplanted to the laboratory and grown in nutrient solutions ranging up to 8 mM Mn. After three weeks, Mn concentration in leaves exceeded 32,000 mu g/g or 3.2%. This result suggests that P. americana possesses a latent physiological ability to hyperaccumulate Mn, even if this trait is rarely, if ever, expressed within its native range.