Root porosity, radial oxygen loss and iron plaque on roots of wetland plants in relation to zinc tolerance and accumulation
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Background and aims
Wetland plants have been widely used in constructed wetlands for the clean-up of metal-contaminated waters. This study investigated the relationship between rate of radial oxygen loss (ROL), root porosity, Zn uptake and tolerance, Fe plaque formation in wetland plants.
A hydroponic experiment and a pot trial with Zn-contaminated soil were conducted to apply different Zn level treatments to various emergent wetland plants.
Significant differences were found between plants in their root porosities, rates of ROL, Zn uptake and Zn tolerance indices in the hydroponic experiment, and concentrations of Fe and Mn on roots and in the rhizosphere in the pot trial. There were significant positive correlations between root porosities, ROL rates, Zn tolerance, Zn, Fe and Mn concentrations on roots and in the rhizosphere. Wetland plants with higher root porosities and ROL tended to have more Fe plaque, higher Zn concentrations on roots and in their rhizospheres, and were more tolerant of Zn toxicity.
Our results suggest that ROL and root porosity play very important roles in Fe plaque formation, Zn uptake and tolerance, and are useful criteria for selecting wetland plants for the phytoremediation of Zn-contaminated waters and soils/sediments.
KeywordsAerenchyma Heavy metal Iron plaque Radial oxygen loss (ROL) Wetland plant Rhizosphere
We sincerely thank Mr. HY Huang (SYSU) and Ms HY Dong (SYSU) for their technical help and Prof AJM Baker (University of Melbourne, Australia) for assisting with the review of this paper. This research was financially supported by the National Natural Science Foundation of China (No. 30570345, 30770417, 41201312), Guangdong Natural Science Foundation (06202438) and State Key Laboratory in Marine Pollution, City University of Hong Kong.
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