Authors: Carla Oporto Erik Smolders Fien Degryse Liesbeth Verheyen Carlo Vandecasteele
Publish Date: 2008/11/15
Volume: 318, Issue: 1-2, Pages: 127-135
Abstract
The technique of diffusive gradients in thin films DGT has been shown to be a promising tool to assess metal uptake by plants in a wide range of soils With the DGT technique diffusion fluxes of trace metals through a diffusion layer towards a resin layer are measured The DGT technique therefore mimics the metal uptake by plants if uptake is limited by diffusion of the free ion to the plant roots which may not be the case at high metal supply This study addresses the capability of DGT to predict cadmium Cd uptake by plants at varying Cd supply To test the performance of DGT in such conditions we used the chloride Cl− enhancement effect ie the increase in Cd solution concentrations—due to chloride complexation of Cd—and Cd uptake with increasing Cl− concentrations as previously characterized in pot field and solution culture experiments The uptake of Cd by spinach was assessed in soil amended with Cd 04–105 mg Cd kg−1 and NaCl up to 120 mM in a factorial design Treatments with NaNO3 were included as a reference to correct for ionic strengths effects The effect of Cl− on the shoot Cd concentrations was significant at background Cd but diminished with increasing soil Cd Increasing Cl− concentrations increased the root area based Cd uptake fluxes by more than a factor of 5 at low soil Cd but had no significant effect at high soil Cd Shortterm uptake of Cd in spinach from nutrient solutions confirmed these trends In contrast increasing Cl− concentrations increased the DGT measured fluxes by a factor of 5 at all Cd levels As a result DGT fluxes were able to explain soil Cl− effects on plant Cd concentrations at low but not at high Cd supply This example illustrates under which conditions DGT mimics trace metal bioavailability If biouptake is controlled by diffusive limitations DGT should be a successful tool for predicting ion uptake across different conditions
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