Author
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Reed, Stewart |
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Ayala-Silva, Tomas |
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Dunn, Christopher - Chris |
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GORDON, GARRY - Us Deparment Of Homeland Security |
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Submitted to: Journal of Agricultural Science
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 2/2/2014 Publication Date: N/A Citation: N/A Interpretive Summary: The Florida Department of Environmental Protection goals for cleanup of arsenic contaminated residential and industrial soils are 0.8 and 3.7 ppm soil, respectively. In Miami, Florida 95% of soils sampled exceeded the residential and 33% exceeded the commercial goal. Soil contaminated with arsenic levels above regulatory goals is a problem for people living in South Florida. Ornamental plants have not been fully investigated as a mechanism for clean-up of low level As contaminated soil. This study evaluates nutrient uptake by ornamental plants grown in a hydroponic system containing concentrations of 0.0, 0.75, 1.5, 3.0, 3.75, 5.25 ppm arsenic. Arsenic toxicity disrupts most plant metabolic functions and can influence uptake of soil nutrients and their redistribution from roots to aboveground plant parts. Essential nutrients calcium, iron, phosphorus and sulfur concentrations initially increase as the plant attempts to detoxify or neutralize the affects of arsenic. As arsenic exposure intensifies, nutrient uptake is disrupted. Plant uptake can no longer supply both detoxification and a normal metabolic need, concentrations of these nutrients inside the plant goes down resulting in reduced growth. Iron deficiency is likely the primary cause of leaf chlorosis, the yellowing of leaves that develops as an early symptom of arsenic toxicity. A reduction in copper concentration is an early effect of arsenic toxicity. Copper is an essential element used in neutralizing highly reactive oxygen free radicals that can damage a plant’s photosynthetic machinery. Differences in mineral uptake reflect the plant’s attempt to detoxify arsenic (i.e. increase in sulfur for arsenic binding sulfur containing proteins), mitigate damage to the cell (i.e. Ca to repair leaky menbranes) or continue cellular functions through alternative pathways (i.e. iron to replace the function of copper and zinc in free radical neutralization). The Florida Department of Environmental Protection goals for cleanup of arsenic contaminated residential and industrial soils are 0.8 and 3.7 mg As kg-1 soil, respectively. In Miami, Florida 95% of soils sampled exceeded the residential and 33% exceeded the commercial goal. Soil contaminated with As levels above regulatory goals is a problem for people living in South Florida. 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 is likely influenced by the toxic effect of As on root functions. Reduced growth limited the demand for Ca, K and Mg and contributed to low uptake. 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 5.25 mg As L-1 only. Tissue Sulfur initially increased then subsequently decreased at 5 mg L-1 As where uptake could no longer supply enough S for both detoxification and normal metabolic needs. The effect of As on plant B status is 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 reductions in Zn, Mn or Mg contributed to chlorosis. Cu use in cellular functions was very efficient. Copper deficiency is one of the initial effects of As toxicity. Arsenic toxicity can influence uptake of soil nutrients and their redistribution inside plant tissue. Calcium, Fe, P and S concentrations tended to increase as the plant attempted to detoxify or neutralize the affects of As. A reduction in Cu conce Technical Abstract: 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 reductions in Zn, Mn or Mg contributed to chlorosis. Copper use in cellular functions was very efficient; never-the-less, 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). Effects of arsenic on nutrient accumulation and distribution in selected ornamental plants Stewart T. Reed, Tomas Ayala-Silva, Christopher B. Dunn, and Garry G. Gordon |
