Authors: Juneja, Shikha; Prakash, Satya

Source: Chemical Speciation and Bioavailability, Volume 17, Number 4, November 2006 , pp. 161-169(9)

Publisher: Science Reviews 2000 Ltd

Abstract:

The toxicity, mobility and bioavailability of Cr, a versatile industrial metal and a contaminant, depends on its chemical form, viz: Cr(III) and Cr(VI). It may enter humans through plants grown on contaminated soil or irrigated by contaminated water. The phytoavailability and transfer through agricultural food chains requires an understanding of mechanisms of Cr uptake and translocation by plants. Xylem sap transports both nutrient and non-nutrient ions after absorption by roots to aerial parts of the plant. It transports cations by complexation with organic ligands. Trivalent chromium, though prone to hydrolysis, also complexes O donor ligands. The chemical form in which Cr(III) is transported by xylem sap was investigated. In vitro studies were performed by mixing the xylem sap of maize plants at three stages of plant growth with radiotagged Cr(III). The speciation change was investigated after 10 days and 30 days by anion and cation exchange elution chromatography. The elution curves were compared with those of pure Cr(III) and Cr(III) complexes of different synthetic acids. Complexation of Cr(III) with ligands of xylem sap especially with carboxylates was evident. Cationic Cr(III) was vitally being transported as anionic organic complex species. The major species seemed to be that of Cr(III)-citrate. Citric acid was the major complexing acid of xylem sap as determined by HPLC. These mobile and soluble complexes may get immobilized and stored in leaves and other edible plant parts. This may also be a mechanism used by plants for detoxification of toxic Cr(VI) which may become reduced and then complexed.

Keywords: Cr(III); xylem sap; citric acid; complexation; ion exchange; transport; plants

Document Type: Research article

DOI: http://dx.doi.org/10.3184/095422906783438820

Affiliations: 1: Department of Chemistry, Dayalbagh Educational Institute, Dayalbagh, Agra-282005, India

Publication date: 2006-11-10

More about this publication?

• Chemical Speciation & Bioavailability covers a rapidly expanding area in environmental science.

  Research on the interactions between the chemical forms and behaviour of toxic compounds and their subsequent biological uptake, metabolism and ecological fate involves many scientific fields. These studies are often published in discipline-specific journals, leading to inadequate review and information scatter. This situation hinders both the development of an international community of experienced colleagues and the open flow of information and discussion. Additionally, the importance of speciation and bioavailability research to the development of pollution law and control technologies is being increasingly appreciated by environmental regulatory agencies throughout the world.

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