Uptake, Distribution, and Speciation of Chromium inBrassica Juncea

Abstract

Brassica juncea (Indian mustard) has been widely used in phytoremediation because of its capacity to accumulate high levels of chromium (Cr) and other metals. The present study was conducted to investigate mechanism(s) involved in Cr binding and sequestration by B. juncea. The plants were grown under greenhouse conditions in field-moist or air-dried soils, amended with 100 mg kg(-1) of Cr (III) or VI). The plant concentrated Cr mainly in the roots. B. juncea removed an average of 48 and 58 microg Cr per plant from Cr (III) and Cr (VI)-treated soils, respectively. The uptake of Cr was not affected by the moisture status of the soils. X-ray absorption near-edge spectroscopy measurements showed only Cr (III) bound predominantly to formate and acetate ligands, in the bulk and rhizosphere soils, respectively. In the plant tissues, Cr (III) was detected, primarily as acetate in the roots and oxalate in the leaves. X-ray microprobe showed the sites of Cr localization, and probably sequestration, in epidermal and cortical cells in the roots and epidermal and spongy mesophyll cells in the leaves. These findings demonstrate the ability of B. juncea to detoxify more toxic Cr (VI), thereby making this plant a potential candidate for phytostabilization.

Response to metal stress of Nicotiana langsdorffii plants wild-type and transgenic for the rat glucocorticoid receptor gene

“…Cr(III) does not show any measurable toxic effect even at several tens of ppm in the culture medium (Moral et al, 1995(Moral et al, , 1996. The efficiency of Cr(III) adsorption by the radical apparatus and the mobility in the plant depend on the presence of complexing agents (James and Bartlett, 1983;Bluskov et al, 2005). Conversely, chromate ions are able to cross the plasmatic membrane and can cause dose-related damages to the plant although most of Cr(VI) is eventually reduced to the less toxic trivalent form.…”

Nickel bioaccumulation by the chosen plant species

“…The so far known species accumulating considerable amounts of heavy metals are generally characterised by a slow seasonal growth, complicated propagation method and small biomass increment, therefore their efficiency in soil cleaning is insufficient (Bluskov et al 2005;Boyd 2004;Yang et al 2005).…”

The Role and Significance of Reference Values in the Identification and Evaluation of Trace Elements from Diet

“…Trivalent Cr is relatively insoluble in water and tends to form hydroxide precipitates with Fe at typical ground water pH values. However, at high concentrations of oxygen or Mn oxides, Cr(III) can be oxidized to Cr(VI) [123,125]. Hexavalent Cr is considered as highly toxic and a potential human carcinogen having detrimental effects on several organs and tissues [123,126].…”