Morphology, ecology, and contaminant removal efficiency of eight wetland plants with differing root systems.

The objective of this study was to test the hypothesis that fibrous-root plants and rhizomatic-root plants are characterized by different root morphologies, root growth and distribution, and contaminant removal capabilities. Four fibrous-root and four rhizomatic-root wetland plants were studied in mono-cultured microcosms which received wastewater. Fibrous-root plants had significantly greater (P < 0.05) small-size root (diameter ≤ 1 mm) biomass and a larger (P < 0.05) root surface area per plant than the rhizomatic-root plants and exhibited accelerated growth in both shoots and roots compared to the rhizomatic-root plants. Fibrous-root plants developed the majority of their root biomass increment within a shallower gravel medium than the rhizomatic-root plants. All plants demonstrated fast root biomass growth from July to September. The wetland microcosms planted with fibrous-root plants showed significantly higher (P < 0.05) ammonium-nitrogen (NH4-N) and nitrate-nitrogen (NO3-N) removal rates from July to December than those planted with the rhizomatic-root plants. These results suggest that root characteristics of wetland plants, which are related to their shoot and root growth, root distribution, and decontamination ability, can be used in the selection of wetland plants with a higher contaminant removal capacity and in the construction of a multi-species wetland plant community.