EFFECTS OF ROOT MORPHOLOGY AND HG CONCENTRATION IN THE SOIL ON UPTAKE BY TERRESTRIAL VASCULAR PLANTS

Vascular plant tissues of various species growing on flood plain soils along the South River at Waynesboro, VA, have previously been shown to contain Hg. These soils characteristically contain 10-20 mu g Hg g(-1). In the field, root/rhizome Hg content in Asclepias syriaca and Solidago sp. ranged from undetectable amounts at low Hg control sites to 1.96 mu g Hg gdw(-1) at contaminated sites, with the association being inversely related to subterranean organ size. Within each size class, tissue Hg was directly related to soil Hg concentration. The relationship of subterranean organ size and enhanced Hg association was further substantiated by high levels of Hg in the fibrous root systems of grasses grown under greenhouse conditions.