How do low doses of desferrioxamine B and EDTA affect the phytoextraction of metals in sunflower?
The aim of this study was to compare the efficiency of siderophore desferrioxamine B (DFOB) and EDTA in increasing the phytoextraction of metals in sunflower. A 28-day pot experiment was conducted in a metal-contaminated soil supplied with 200μmolkg-1of DFOB or EDTA. Pore water was collected and pseudo-polarographic analyses were conducted to assess the impact of the two chelators on the mobility and speciation of metals in the liquid phase. Our results showed that DFOB is not an efficient mobilizing agent of divalent metals in soil. Adding DFOB selectively increased the mobility of trivalent metals while the supply of EDTA simultaneously increased the mobility of both trivalent and divalent metals. EDTA significantly reduced the labile fractions of Cd, Cu, (Pb) and Zn measured in the porewater. The labile concentration of Cd and Zn measured in presence of EDTA was even less than that measured in the control. As expected from the pore water analysis, the addition of DFOB did not affect the phytoextraction of any divalent metals. In contrast, the addition of EDTA enhanced Cu and Ni phytoextraction in sunflower 2.0 to 2.8 fold for Cu and 1.3 to 2.3 fold for Ni, depending on the cultivar. This result supports different hypotheses regarding the forms and the related pathways in which metals are taken up in presence of EDTA. Based on the results obtained for Ni, whose uptake is rate limited by its internalization across the cell membrane, the direct uptake of metal-EDTA complexes via the non-selective apoplastic pathway is hypothesized to contribute the most to the overall uptake of metals in presence of EDTA, even added at "low" concentrations.
ISPA, Bordeaux Sciences Agro, INRA, 33140 Villenave d'Ornon, France. Electronic address: jean-yves.cornu@inra.fr.
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Cornu
ISPA, Bordeaux Sciences Agro, INRA, 33140 Villenave d'Ornon, France.
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Dépernet
PROTEE, Université de Toulon, CS 60584, 83041 Toulon cedex 9, France.
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Garnier
PROTEE, Université de Toulon, CS 60584, 83041 Toulon cedex 9, France.
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Lenoble
LPG-NANTES, UMR 6112 CNRS, Université de Nantes, 44322 Nantes, France.
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Braud
LPG-NANTES, UMR 6112 CNRS, Université de Nantes, 44322 Nantes, France.
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Lebeau
D001673:Biodegradation, Environmental; D002614:Chelating Agents; D003676:Deferoxamine / Q000494:pharmacology*; D004492:Edetic Acid / Q000494:pharmacology*; D006368:Helianthus / Q000187:drug effects* / Q000378:metabolism; D019216:Metals, Heavy / Q000302:isolation & purification*; D012989:Soil Pollutants / Q000302:isolation & purification*
D002614:Chelating Agents; D019216:Metals, Heavy; D012989:Soil Pollutants; D004492:Edetic Acid; D003676:Deferoxamine
Bacterial siderophore; Between-cultivar variability; Complexation; Phytoavailability; Pseudo-polarography; Soil