Uptake and apoplastic retention of EDTA‐ and phytosiderophore‐chelated chromium(III) in maize

Abstract

Increasing the mobilization and root uptake of chromium (Cr) by synthetic and plant-borne chelators might be relevant for the design of phytoremediation strategies on Cr-contaminated sites. Short-term uptake studies in maize roots supplied with 51 CrCl 3 or 51 Cr(III)-EDTA led to higher apoplastic Cr contents in plant roots supplied with 51 CrCl 3 and in Fesufficient plants relative to Fe-deficient plants, indicating that Fe stimulated co-precipitation of Cr. Concentration-dependent retention of Cr in a methanol:chloroform-treated cell-wall fraction was still saturable and in agreement with the predicted tendency of Cr(III) to precipitate as Cr(OH) 3 . To investigate a possible stimulation of Cr(III) uptake by phytosiderophores, Fe-deficient maize roots were exposed for 6 d to Cr(III)-EDTA or Cr(III)-DMA (2'-deoxymugineic acid). Relative to plants without Cr supply, the supply of both chelated Cr species in a subtoxic concentration of 1 lM resulted in alleviation of Fe deficiency-induced chlorosis and higher Cr accumulation. Long-term Cr accumulation from Cr(III)-DMA was similar to that from Cr(III)-EDTA, and Cr uptake from both chelates was not altered in the maize mutant ys1, which is defective in metal-phytosiderophore uptake. We therefore conclude that phytosiderophores increase Cr solubility similar to synthetic chelators like EDTA, but do not additionally contribute to Cr(III) uptake from Cr-contaminated sites.

The effect of organic compounds in the oxidation kinetics of Cr(III) by H2O2

“…Complexing times adopted by previous workers (Srivastava et al, 1999;Anis, 2001;Tzou et al, 2002;Giusti and Barakat, 2005;Threeprom et al, 2005;Erenoglu et al, 2007) result to vary from hours to many days, although Cr(III) concentrations explored in these previous studies were generally higher than ours by 1 to 2 orders of magnitude. These time scales were comparable to those used in our study.…”

“…Soluble complexes also could be formed outside the cell via interaction of freshly formed Cr(III), for example by the reduction of Cr(VI) with photochemically produced Fe(II) (Kaczynski and Kieber, 1993), with organics. Organo-Cr(III) species increase the mobilization of chromium and play a relevant role either in phytoremediation strategies by increasing Cr uptake by plants (Erenoglu et al, 2007) or in microbial bioremediation of Cr(VI) contaminated sites by increasing the risk of Cr(III) migration in groundwater (Puzon et al, 2005).…”

Bio-concentration of chromium—an in situ phytoremediation study at South Kaliapani chromite mining area of Orissa, India

“…The aerial parts of the plants showed ten to 100-fold less Cr S4 S5 S6 S9 S10 S11 S14 S15 S20 BT as compared to roots. Similar types of result were also reported earlier by several workers (Zayed and Terry 2003;Pulford and Watson 2003;Ghosh and Singh 2005a;Dong et al 2007;Zhang et al 2007;Erenoglu et al 2007). High bioavailability of metals in roots and low translocation to shoots is the most common resistance trait (Zayed and Terry 2003;Dickinson and Lepp 1997).…”

Kinetics of oxidation of Cr(III)-organic complexes by H2O2

“…Numerous investigators have provided evidence for the existence of Cr(III)-organic complexes under environmental conditions (Harris, 1977;Nakayama et al, 1981;Ahern et al, 1985;Davis et al, 1994;Kaczynskl et al, 1994;Fukushima et al, 1995;Zhitkovich et al, 1995Zhitkovich et al, , 1996Mattuck and Nikolaidis, 1996;Sule and Ingle, 1996;Walsh and O'Halloran, 1996;Quievryn et al, 2002;Howe and Loeppe, 2003;Puzon et al, 1997Puzon et al, , 2005Puzon et al, , 2008. Organo -Cr(III) species increase the mobilisation of chromium and play a relevant role either in phyto-remediation strategies by increasing Cr uptake by plants (Erenoglu et al, 2007) or in microbial bioremediation of Cr(VI) contaminated sites by increasing the risk of Cr(III) migration in groundwater (Puzon et al, 2005).…”