Abstract
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.
Highlights
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
Arsenic-based pesticides, herbicides and insecticides have contaminated a large amount of acreage on turf-farms, orchards, and around greenhouses, shadehouses and other horticultural production structures (Woolson Axley, & Kearney, 1971; Murphy & Aucott, 1998)
Based on a rapid reduction in dry weight with exposure to As, coreopsis and tithonia were plants that proved to be very sensitive to As
Summary
Arsenic-based pesticides, herbicides and insecticides have contaminated a large amount of acreage on turf-farms, orchards, and around greenhouses, shadehouses and other horticultural production structures (Woolson Axley, & Kearney, 1971; Murphy & Aucott, 1998). Occurring soil As can range from 1-40 mg As kg-1 soil (Walsh Sumner, & Keeney, 1977), contaminated levels can reach as high as 2600 mg As kg-1 soil (Meharg Naylor, & Macnair, 1994). Arsenic is not an essential element for plant nutrition (Marin Masscheleyn, & Patrick, 1993) and conducts no known metabolic function. Plants vary in their ability to tolerate As (Meharg, 1994). The reduced form of As, is likely taken up by aquaporin channels in plant roots (Meharg & Jardine, 2003). Rice (Oryza sativa, L.) (Marin, Masscheleyn, & Patrick, 1992; Ma et al, 2008), cucumber (Cucumis sativus L.) (Mihucz et al, 2005), Brassica juncea (Pickering et al, 2000), tomato (Lycopersicum esculentum) (Burló Guijarro, Carbonell-Barrachina, Valero, & Martinez-Sanchez, 1999), Spartina patens and Spartina alterniflora (Carbonell-Barrachina, Aarabi, DeLaune, Gambrell, & Patrick, 1998), reduce arsenate to arsenite in the root, very little As is translocated from root to shoot
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