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Mineralogy of Pb-P grains in the roots of Agrostis capillaris L. by ATEM and EXAFS*

Published online by Cambridge University Press:  05 July 2018

J. D. Cotter-Howells
Affiliation:
Department of Earth Sciences, The University of Manchester, Manchester M13 9PL, UK School of Biological Sciences, The University of Manchester, Manchester M13 9PL, UK
P. E. Champness
Affiliation:
Department of Earth Sciences, The University of Manchester, Manchester M13 9PL, UK
J. M. Charnock
Affiliation:
Department of Earth Sciences, The University of Manchester, Manchester M13 9PL, UK CLRC Daresbury Laboratory, Warrington WA4 4AD, UK

Abstract

Analytical transmission electron microscopy (ATEM) and X-ray absorption spectroscopy (XAS) have been used to determine the mineralogy of Pb-P deposits in the roots of the heavy metal tolerant grass cultivar Agrostis capillaris L. cv. Parys Mountain. The deposits have a pyromorphite (Pb5(PO4)3Cl)-type structure and composition although some of the Cl may be substituted by OH. Energy-dispersive mapping under the scanning electron microscope demonstrated that the majority of these deposits are present in the outer cell wall of the epidermis (the outermost layer of root cells). The phosphate composition of these grains contrasts with the phytate (C6H18O24P612−) composition of Zn-P deposits observed in similar electron microscopy studies. The physiological role of heavy metal P deposits is unclear. Heavy metal P precipitates may form actively as a tolerance mechanism to heavy metals or passively, sequestering P in a metabolically inactive form.

Type
Research Article
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1999

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Footnotes

Present address: Department of Plant and Soil Science, Cruickshank Building, Aberdeen University, Aberdeen AB24 3UU, UK.

*

The first four papers in this issue were presented at the Mineralogical Society's Spring Meeting, held on 18th March 1997, entitled ‘Phosphates: biogenic to exotic’

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