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(131) Uptake of Labile and Nonlabile Selenium by Various Plant Taxa.
Goodson, Christopher1, Parker, David*,1, Amrhein, Christopher1, Zhang, Yiqiang, 1 University of California, Riverside, CA
ABSTRACT- Phytoremediation of Se-contaminated soils and sediments may be more feasible if hyperaccumulating taxa are identified that can effectively extract the more refractory forms of Se present. The capacity of six plant genotypes to take up labile and nonlabile soil Se was evaluated using isotopic dilution methods. Five high-Se soils were amended with 75Se at a rate of 400 to 700 kBq/kg soil, and placed in PVC columns in the greenhouse. Seeds of Astragalus bisulcatus, A. canadenis, Brassica juncea, Sporobolus airoides, and Stanleya pinnata (two ecotypes) were seeded directly, harvested, and analyzed for both "cold" Se and 75Se to allow computation of L values. The labeled soils were extracted KCl and similarly analyzed to yield E values, which ranged from <5 to 65% of the indigenous soil Se. None of the plants tested yielded L values that were consistently greater than the E values, suggesting that all plants, including Se-hyperaccumulators, access the same labile pool of Se. The Se extractable with either KCl or a neutral phosphate salt was highly correlated with radiolabile Se (the E value), indicating that simple chemical extractions can accurately estimate the bioavailable fraction of soil Se. Other root-growth experiments in rhizoboxes using Se-spiked soil were performed. In contrast to other reports concerning Ni hyperaccumulators, none of the Se-accumulating taxa demonstrated any marked preferential root growth in the discrete zones of Se-amended soil.
Key words: selenium, phytoremediation, hyperaccumulators, isotopic dilution
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