Rhizosphere pH gradient controls copper availability in a strongly acidic soil
Using a root mat approach, we quantified how root-induced alkalization controlled the establishment of copper (Cu) gradients in the rhizosphere of durum wheat (Triticum turgidum durum L.) cropped in a strongly acidic, Cu-contaminated soil. Rhizosphere pH increased over 6 mm in soil, reaching up to+2.8 units close to root mat surface. Conversely, free Cu2+ activity decreased by 3 orders of magnitude and total Cu concentration by 3-fold in the rhizosphere solution, while labile Cu assessed by DGT (diffusive gradients in thin films) was halved. The DIFS (DGT-induced flux in soils and sediments) model failed to adequately simulate Cu depletion in the rhizosphere solution, showing that root-induced alkalization almost entirely explained Cu depletion while plant uptake had little impact. We modeled the observed pH gradient to recalculate its radial extension around a single root. The gradient of free Cu2+ activity in solution, deduced from pH modeling, extended over 1-4 mm in the rhizosphere depending on root radius and OH- efflux from root. Rhizosphere alkalization dramatically decreased root exposure to Cu, substantiating that root-induced chemical changes in the rhizosphere should be better accounted for to assess metal bioavailability to plants.
| Main Authors: | , , , |
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| Format: | article biblioteca |
| Language: | eng |
| Subjects: | P33 - Chimie et physique du sol, F01 - Culture des plantes, P02 - Pollution, Triticum turgidum, cuivre, rhizosphère, disponibilité d'élément nutritif, pH du sol, relation plante sol, alcalinisation, sol pollué, sol acide, http://aims.fao.org/aos/agrovoc/c_7958, http://aims.fao.org/aos/agrovoc/c_1868, http://aims.fao.org/aos/agrovoc/c_6569, http://aims.fao.org/aos/agrovoc/c_5268, http://aims.fao.org/aos/agrovoc/c_34901, http://aims.fao.org/aos/agrovoc/c_16146, http://aims.fao.org/aos/agrovoc/c_35355, http://aims.fao.org/aos/agrovoc/c_34324, http://aims.fao.org/aos/agrovoc/c_89, http://aims.fao.org/aos/agrovoc/c_3081, |
| Online Access: | http://agritrop.cirad.fr/550620/ http://agritrop.cirad.fr/550620/1/document_550620.pdf |
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