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Distribution and speciation of Mn in hydrated roots of cowpea at levels inhibiting root growth

Authors

  • Peter M. Kopittke,

    Corresponding author
    1. Cooperative Research Centre for Contamination Assessment and Remediation of the Environment (CRC-CARE), Salisbury South, South Australia, Australia
    • The University of Queensland, School of Agriculture and Food Sciences, St. Lucia, Queensland, Australia
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  • Enzo Lombi,

    1. Cooperative Research Centre for Contamination Assessment and Remediation of the Environment (CRC-CARE), Salisbury South, South Australia, Australia
    2. University of South Australia, Centre for Environmental Risk Assessment and Remediation, Mawson Lakes, South Australia, Australia
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  • Brigid A. McKenna,

    1. The University of Queensland, School of Agriculture and Food Sciences, St. Lucia, Queensland, Australia
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  • Peng Wang,

    1. The University of Queensland, School of Agriculture and Food Sciences, St. Lucia, Queensland, Australia
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  • Erica Donner,

    1. Cooperative Research Centre for Contamination Assessment and Remediation of the Environment (CRC-CARE), Salisbury South, South Australia, Australia
    2. University of South Australia, Centre for Environmental Risk Assessment and Remediation, Mawson Lakes, South Australia, Australia
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  • Richard I. Webb,

    1. The University of Queensland, Australian Institute for Bioengineering and Nanotechnology, Centre for Microscopy and Microanalysis, St Lucia, Queensland, Australia
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  • F. Pax C. Blamey,

    1. The University of Queensland, School of Agriculture and Food Sciences, St. Lucia, Queensland, Australia
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  • Martin D. de Jonge,

    1. Australian Synchrotron, Clayton, Victoria, Australia
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  • David Paterson,

    1. Australian Synchrotron, Clayton, Victoria, Australia
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  • Daryl L. Howard,

    1. Australian Synchrotron, Clayton, Victoria, Australia
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  • Neal W. Menzies

    1. The University of Queensland, School of Agriculture and Food Sciences, St. Lucia, Queensland, Australia
    2. Cooperative Research Centre for Contamination Assessment and Remediation of the Environment (CRC-CARE), Salisbury South, South Australia, Australia
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Correspondence

Corresponding author,

e-mail: p.kopittke@uq.edu.au

Abstract

The phytotoxicity of Mn is important globally due to its increased solubility in acid or waterlogged soils. Short-term (≤24 h) solution culture studies with 150 µM Mn were conducted to investigate the in situ distribution and speciation of Mn in apical tissues of hydrated roots of cowpea [Vigna unguiculata (L.) Walp. cv. Red Caloona] using synchrotron-based techniques. Accumulation of Mn was rapid; exposure to 150 µM Mn for only 5 min resulting in substantial Mn accumulation in the root cap and associated mucigel. The highest tissue concentrations of Mn were in the root cap, with linear combination fitting of the data suggesting that ≥80% of this Mn(II) was associated with citrate. Interestingly, although the primary site of Mn toxicity is typically the shoots, concentrations of Mn in the stele of the root were not noticeably higher than in the surrounding cortical tissues in the short-term (≤24 h). The data provided here from the in situ analyses of hydrated roots exposed to excess Mn are, to our knowledge, the first of this type to be reported for Mn and provide important information regarding plant responses to high Mn in the rooting environment.

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