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In Miami, Florida, 95% of residential and 33% commercial soils exceed the Florida Department of Environmental Protection goals for cleanup of arsenic contamination. Ornamental plants have not been fully investigated as a mechanism for phytoremediation of low level As contaminated soil. This study evaluates nutrient uptake by ornamental plants grown in a hydroponic system containing concentrations of 0, 10, 20, 30, 40, 50 or 70 uM As (0.0, 0.75, 1.5, 3.0, 3.75, 5.25 mg•L −1 As, respectively). Uptake of Ca, K, Mg and Mo was likely influenced by the toxic effect of As on root functions. Arsenic had little effect on Ca, K and Mg transportation to the shoot at any but the highest As exposure rate. Tissue P concentration was similar to or higher than that found in controls and As competition with P uptake occurred at 70 uM As only. Tissue sulfur initially increased then subsequently decreased at 70 uM As where uptake could no longer supply enough S for both detoxification and normal metabolic needs. The effect of As on plant B was likely a result of membrane leakage and overall tissue damage leading to a reduction in transpiration. Arsenic induced Fe deficiency was likely the primary cause of chlorosis; however, As induced reduction in Zn, Mn or Mg contributed to chlorosis. Copper use in cellular functions was very efficient; nevertheless, Cu deficiency was one of the initial effects of As toxicity. Differences in mineral uptake reflect the plant's attempt to detoxify As (i.e. increase in S for S-containing As chelators), mitigate damage to the cell (i.e. Ca to repair leaky menbranes) or continue cellular functions through alternative pathways (i.e. Fe superoxide dismutases to replace the function of Cu/ZnSOD).

Arsenic-based pesticides, herbicides and insecticides are used in horticultural operations resulting in soil contamination around greenhouse structures. Phytoremediation and phytostabilization are two techniques for treating arsenic (As) contaminated soil. Several ornamental plant species, Iris (Iris savannarum), switchgrass (Panicum virgatum), Tithonia rotundiflora, Coreopsis lanceolata, sunflower (Helianthus annuus), and marigold (Tagetes erecta), were evaluated for their potential use as accumulator plants. Based on dry weight, tithonia and coreopsis were most sensitive to As. Tithonia had an 85% reduction in dry weight at 0.75 mg As L -1 and coreopsis a 65% reduction at 2.25 mg As L -1 solution concentration. Iris dry weight increased with increasing solution concentrations but As did not accumulate in tissue. At the high As rate, marigold and sunflower had uptake ratios of 7.4 and 16.6, respectively, and translocation factors near one. Both show little effect of As toxicity on dry weights production, therefore, are appealing candidates for phytoremediation and phytostabilization. Switchgrass and iris can be harvested multiple times a year, making them candidates for phytostabilization. Keywords: arsenic, iris, marigold, sunflower, switchgrass, translocation factor, uptake ratio Abbreviations Translocation factor: TF = shoot As / root As in mg As kg -1 plant dry weight; uptake ratio: UR = mg As kg -1 plant dry weight/ solution As concentration in mg L -1

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.