Cadmium uptake by durum wheat in presence of citrate

Panfili, Frédéric; Schneider, A.; Vives, Alain; Perrot, F.; Hubert, P.; Pellerin, Sylvain

doi:10.1007/s11104-008-9782-2

Cited by 46 publications

(33 citation statements)

References 39 publications

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“…Lignin accumulation has also been described as a consequence of Cu toxicity (Lequeux et al, 2010) but whether this is related to a heavy metal defence mechanism is still not clear. Zorrig et al (2010) suggested a transport role for citrate to translocate Cd from the roots to the shoots of lettuce plants while Panfili et al (2009) also studied the effect of citrate in the uptake of Cd. Citrate and malate have been reported to be major ligands for Zn and Ni in several studies (Haydon & Cobbett, 2007).…”

Section: Other Non Enzymatic Substances Involved In Heavy Metal Tolermentioning

confidence: 99%

Characterization of Plant Antioxidative System in Response to Abiotic Stresses: A Focus on Heavy Metal Toxicity

Mourato¹,

Reis²,

Martins³

2012

Advances in Selected Plant Physiology Aspects

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Section: Other Non Enzymatic Substances Involved In Heavy Metal Tolermentioning

confidence: 99%

Characterization of Plant Antioxidative System in Response to Abiotic Stresses: A Focus on Heavy Metal Toxicity

Mourato¹,

Reis²,

Martins³

2012

Advances in Selected Plant Physiology Aspects

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“…Only in treatments with very high degree of buffering, this passive uptake was estimated to have a large contribution to the overall uptake. , and Triticum turgidum (Panfili et al, 2009). Usually, two hypotheses are given that may explain this contribution of complexes to the uptake: (1) the uptake is rate limited by diffusion of the free ion to the site of uptake and the presence of complexes increases the diffusive supply, or (2) the complexes are directly taken up.…”

mentioning

confidence: 99%

Diffusion Limitations in Root Uptake of Cadmium and Zinc, But Not Nickel, and Resulting Bias in the Michaelis Constant

et al. 2012

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It has long been recognized that diffusive boundary layers affect the determination of active transport parameters, but this has been largely overlooked in plant physiological research. We studied the short-term uptake of cadmium (Cd), zinc (Zn), and nickel (Ni) by spinach (Spinacia oleracea) and tomato (Lycopersicon esculentum) in solutions with or without metal complexes. At same free ion concentration, the presence of complexes, which enhance the diffusion flux, increased the uptake of Cd and Zn, whereas Ni uptake was unaffected. Competition effects of protons on Cd and Zn uptake were observed only at a very large degree of buffering, while competition of magnesium ions on Ni uptake was observed even in unbuffered solutions. These results strongly suggest that uptake of Cd and Zn is limited by diffusion of the free ion to the roots, except at very high degree of solution buffering, whereas Ni uptake is generally internalization limited. All results could be well described by a model that combined a diffusion equation with a competitive Michaelis-Menten equation. Direct uptake of the complex was estimated to be a major contribution only at millimolar concentrations of the complex or at very large ratios of complex to free ion concentration. The true K m for uptake of Cd 2+ and Zn 2+ was estimated at ,5 nM, three orders of magnitude smaller than the K m measured in unbuffered solutions. Published Michaelis constants for plant uptake of Cd and Zn likely strongly overestimate physiological ones and should not be interpreted as an indicator of transporter affinity.Internalization of metals by biota is traditionally described by Michaelis-Menten kinetics (Wilkinson and Buffle, 2004). The K m corresponds to the concentration in solution at which the uptake is one-half of the maximal uptake, F max . The Michaelis-Menten equation relates the uptake flux, F, to the free ion concentration at the site of uptake, [M] s :If diffusion of a metal across a diffusive boundary layer adjacent to the roots is the rate-limiting step for uptake, the concentration at the site of uptake will be lower than that in the bulk solution. As a result, diffusion limitations result in an overestimate of the K m , if the concentration at the root surface is assumed to be the same as in the bulk solution, as is usually done. This bias in K m has been discussed in detail by Winne (1973) and has, for instance, been demonstrated experimentally for uptake of Glc in rabbit jejunum (Thomson and Dietschy, 1980) and for uptake of several sugars, amino acids, and bile acids in rat ileum (Wilson and Dietschy, 1974).Models used to predict ion availability and toxicity of metals by plants usually rely on the assumption that uptake is controlled by the free metal ion activity and the activity of competing ions in the bulk solution. For instance, the biotic ligand model (BLM), originally developed to predict metal toxicity to aquatic organisms, assumes that toxicity of an ion is mitigated by the presence of competing ions that bind on the biotic ligand (Paqu...

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“…The plants were germinated on filter paper for 5 days and then hydroponically grown for three weeks in a greenhouse at a 24-14 8C day-night cycle with 16 4 and 0.2 mM ZnSO 4 ) was used, buffered with 2.5 mM 3-(N-morpholino)propanesulfonic acid (MOPS) and adjusted with 1 M NaOH to a pH between 6.5 and 6.9. During the whole growth period, the solutions were well aerated.…”

Section: Plant Experimentsmentioning

confidence: 99%

“…After the experimental treatments, the plants were washed for 30 s with ice-cold ultrapure water, immersed for 15 min in an ice-cold desorption bath (background solution plus 100 mM ZnSO 4 ) to replace 65 Zn adsorbed at the root surface, and washed again for 30 s in ice-cold ultrapure water (adapted from Hart et al [13] and Panfili et al [4] ). It can be assumed that Zn uptake stopped when the plants were immersed into the ice-cold water, since Hacisalihoglou et al [14] found that Zn uptake by wheat was negligible from solutions at 2 8C compared to uptake from the same solutions at 23 8C.…”

Section: Post-experimental Treatmentmentioning

confidence: 99%

“…If the supply of free metal to the roots limits the uptake rate, then the dissociation of complexes may add substantially to its uptake, [2] and this contribution is expected to increase with the lability of the complexes. [3,4] On the other hand, the uptake of intact complexes may also contribute to the uptake of metals by plants as found not only for liposoluble [5] but also for uncharged water-soluble complexes. [6] Apart from the chemical nature of the complexes, their physiological role also needs to be considered in this context, as the uptake of Fe and Zn phytosiderophore complexes by grasses illustrates.…”

Section: Introductionmentioning

confidence: 99%

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Diffusion limitation of zinc fluxes into wheat roots, PLM and DGT devices in the presence of organic ligands

et al. 2014

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Environmental context. Zinc is an essential micronutrient for plants and many arid areas of the world have zinc-deficient soils. The bioavailability of Zn to plants is influenced by diffusion limitations and complex lability in the soil solution. To identify the relative importance of these two factors, we investigated the influence of diffusion layer thickness on Zn uptake by wheat and by two bio-mimetic devices in the presence of ethylenediaminetetraacetic acid and two natural ligands found in soil.Abstract. Organic ligands can increase metal mobility in soils. The extent to which this can contribute to plant metal uptake depends among others, on complex lability and diffusion limitations in solute transfer from the soil solution to root uptake sites. We investigated the influence of diffusion layer thickness on zinc uptake by wheat seedlings in the presence of ethylenediaminetetraacetic acid (EDTA), citrate and histidine with similar free Zn by measuring 65 Zn uptake from stirred, non-stirred and agar-containing solutions. Analogous experiments were performed using permeation liquid membranes (PLM) and 'diffusive gradients in thin films' (DGT) probes as bio-mimetic devices. In treatments with low EDTA concentrations (,2 mM) or ligand-free Zn solution, increasing diffusion layer thickness reduced Zn fluxes into roots to a similar extent as into PLM and DGT probes, indicating reduced uptake attributable to diffusion limitation. In the citrate treatments root Zn influx was similar to EDTA treatments under stirred conditions, but increasing diffusion layer thickness did not affect Zn uptake. This suggests complex dissociation compensated for reduced Zn 2þ diffusion and that the entire complexes were not taken up. The Zn root influxes in the histidine treatments were found to be on average by a factor of 2.5 higher than in the citrate treatments and they also showed no decrease in non-stirred and agar treatments. Dissociation kinetics inferred from PLM measurements explained a large part, although not all, of the increased Zn uptake by the plants in the presence of histidine. The difference may be a result of the uptake of neutral or positive Zn-histidine complexes. The results of this study confirm that labile complexes can contribute to Zn uptake by wheat either through diffusion limitation and complex dissociation or through uptake of entire complexes, depending on the nature of the ligands.

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Cadmium uptake by durum wheat in presence of citrate

Cited by 46 publications

References 39 publications

Characterization of Plant Antioxidative System in Response to Abiotic Stresses: A Focus on Heavy Metal Toxicity

Characterization of Plant Antioxidative System in Response to Abiotic Stresses: A Focus on Heavy Metal Toxicity

Diffusion Limitations in Root Uptake of Cadmium and Zinc, But Not Nickel, and Resulting Bias in the Michaelis Constant

Diffusion limitation of zinc fluxes into wheat roots, PLM and DGT devices in the presence of organic ligands

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