Evidence for nickel mobilisation in rhizosphere soils of Ni hyperaccumulator Odontarrhena serpyllifolia

Rhizosphere processes are known to modify uptake of elements from soil, but limited information is available for hyperaccumulators. We investigated labile Ni fractions and their kinetics replenishment in the rhizospheres Ni-hyperaccumulator Odontarrhena serpyliffolia, Ni-excluder Holcus lanatus bulk soils collected at same serpentine outcrop. Labile rhizosphere soil were evaluated using conventional extractions also by Diffusive Gradients Thin Films (DGT) technique. DGT data used predict resupply DIFS modelling. Chemical imaging distribution along roots coupled with laser-ablation was conducted. forms higher both than soils, together an increase dissolved organic C, cation exchange capacity Ca/Mg ratio. fractionation indicated a shift towards less stable rhizosphere, particularly hyperaccumulator. modelling showed that excluder able sustain initially lower soluble concentration through solid phase, while hyperaccumulator not sufficient maintain high concentrations Ni. However, amount DGT-labile compared all deployment times. Our suggest compounds derived root activity, particular DOC, important controls availability plants growing on soil.