Effects of iron plaque on phosphorus uptake by Pilea cadierei cultured in constructed wetland

Iron plaque often forms in the root surfaces of aquatic and terrestrial plant species. However, little is known about the role of iron plaque in controlling phosphate (P) movement from soil or water to the aboveground part of a wetland plant. This study, based on a constructed wetland model system, systematically investigat-ed the influence of iron plaque on phosphorus uptake by and accumulation in a typical wetland plant named as Pilea cadierei. Plants were treated with Fe and P at a loading rate of 0,500 or 1000 mg Fe kg−1 soil and 0, 5, 10, 50 or 100 mg P L−1 simulated waste water. Study results demonstrated iron plaque on the root surface is not a barrier to P uptake & translocation within Pilea cadierei, and iron plaque concentrations in Dithionite-Citrate-Bicarbonate (DCB) extracts were significantly affected by the input level of P and Fe. Moreover, the P concentration in DCB-extracts and in roots and shoots were also significantly affected by the input level of P and Fe. Higher loading level of Fe and P renders iron plaque a higher capacity to adsorb phosphorus.