Comparison of corn and lupin in respect to As mobilisation, uptake and release in an arsenic contaminated floodplain soil.

Based on the differences of lupin and corn in Si requirement and their capacity to release organic acids for P mobilisation both plant species were compared in respect to As mobilisation and plant As uptake and release which is closely linked to P and Si nutrition.Plants were grown with and without P fertilization in an As contaminated floodplain soil in compartment systems which enabled temporally resolved sampling of soil solution with increasing distance from the root surface.Although no direct increase of P or AsV concentration in soil solution could be detected, lupins showed higher P and As uptake but lower root to shoot translocation of As compared to corn plants. Higher root As concentrations in lupins corresponded to higher AsIII concentration in soil solution which increased with time and corresponded to the recently demonstrated diffusion driven efflux of As in the form of AsIII via aquaglycerol channels. It is well established that AsV, the form of As initially present in the floodplain soil, is taken up via P transporters. Hence the higher As uptake of lupin is in line with previous results showing higher P uptake capacity per unit root length for lupin compared to corn. A lower capacity for As efflux in lupin as it was expected due to lower Si requirement of lupin compared to corn could not be demonstrated.