Organic acids promote the uptake of lanthanum by barley roots

Authors

  • Fang Han,

    1. Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, PO Box 2871, Beijing 100085, China;
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  • Xiao-Quan Shan,

    Corresponding author
    1. Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, PO Box 2871, Beijing 100085, China;
      Author for correspondence: Xiao-Quan Shan Tel: +86 10 62923560 Fax: +86 10 62923563 Email: xiaoquan@mail.rcees.ac.cn
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  • Jing Zhang,

    1. State Key Laboratory of Synchrotron Radiation, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100039, China
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  • Ya-Ning Xie,

    1. State Key Laboratory of Synchrotron Radiation, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100039, China
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  • Zhi-Guo Pei,

    1. Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, PO Box 2871, Beijing 100085, China;
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  • Shu-Zhen Zhang,

    1. Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, PO Box 2871, Beijing 100085, China;
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  • Yong-Guan Zhu,

    1. Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, PO Box 2871, Beijing 100085, China;
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  • Bei Wen

    1. Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, PO Box 2871, Beijing 100085, China;
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Author for correspondence: Xiao-Quan Shan Tel: +86 10 62923560 Fax: +86 10 62923563 Email: xiaoquan@mail.rcees.ac.cn

Summary

  • • Organic acids play an important role in metal uptake by, and accumulation in, plants. However, the relevant mechanisms remain obscure.
  • • Acetic, malic and citric acids increased the uptake of lanthanum (La) by barley (Hordeum vulgare) roots and enhanced La content in shoots under hydroponic conditions.
  • • Concentration-dependent net La influx in the absence and presence of organic acids yielded nonsaturating kinetic curves that could be resolved into linear and saturable components. The saturable component followed Michaelis–Menten kinetics. The Km values were similar; however, the Vmax values in the presence of acetic, malic and citric acids were 4.3, 2.8, 1.5-times that of the control, respectively.
  • • Enhanced uptake of La by organic acids was mediated mainly, but not solely, by Ca2+ channels. X-ray absorption spectroscopic techniques provided evidence of La–oxygen environment and established that La(III) was coordinated to 11 oxygen atoms that are likely to be involved in the binding of La(III) to barley roots via carboxylate groups and hydration of La(III).

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