Nutrient Uptake of Ornamental Plants Exposed to Arsenic in Hydroponic Solution

Arsenic-based agro-chemicals have contaminated considerable acreage on turf-farms, orchards, and around horticultural production structures. A study was undertaken to evaluate iris (Iris savannarum), switchgrass (Panicum virgatum), Tithonia rotundiflora, Coreopsis lanceolata, sunflower (Helianthus annuus), and marigold (Tagetes erecta) for their potential use as arsenic (As) accumulator plants. Plants were grown hydroponically with a modified Hoagland solution containing either 0, 10, 50 or 70 uM As (0.0, 0.75, 3.75, 5.25 mg L-1, respectively). At 5.25 mg As L-1 solution there were no significant reductions in dry weight below that of the controls for iris marigold and sunflower. Maximum shoot As content (mg) for coreopsis and tithonia was reached at 0.75 and for switchgrass at 3.75 mg As L-1 solution. Iris marigold and sunflower maximum shoot As levels occurred at a solution concentration above 5.25 mg As L-1 solution, the high level used in this study. In general P decreased and S increased with increasing solution As. Marigold, switchgrass and sunflower, species that tolerated As at the levels used in this study, had a weak negative correlation between As and Cu concentrations in common. In these species As in hydroponic solution had no effect, or even slightly enhanced, P uptake compared to controls. Arsenic sensitive species coreopsis and tithonia had weak negative correlations between As and K and P in common. Coreopsis and tithonia appears to have a competitive uptake mechanism between arsenate with phosphate. Arsenic tolerance in iris appears to be a result of prohibiting As accumulation in root tissue.