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Protozoa enhance foraging efficiency of arbuscular mycorrhizal fungi for mineral nitrogen from organic matter in soil to the benefit of host plants

Authors

  • Robert Koller,

    Corresponding author
    1. Universität zu Köln, Zoologisches Institut, Abt. Terrestrische Ökologie, Köln, Germany
    • Université de Lorraine UMR 1121 INRA Agronomie et Environnement Nancy-Colmar, Vandoeuvre-lès-Nancy, France
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  • Alia Rodriguez,

    1. Universidad Nacional de Colombia, Sede Bogotá Ciudad Universitaria - Avenida Carrera 30 no. 45-03, Bogotá, Colombia
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  • Christophe Robin,

    1. Université de Lorraine UMR 1121 INRA Agronomie et Environnement Nancy-Colmar, Vandoeuvre-lès-Nancy, France
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  • Stefan Scheu,

    1. J.F. Blumenbach Institute of Zoology and Anthropology, Georg August University Göttingen, Göttingen, Germany
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    • These authors contributed equally to this work.
  • Michael Bonkowski

    1. Universität zu Köln, Zoologisches Institut, Abt. Terrestrische Ökologie, Köln, Germany
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    • These authors contributed equally to this work.

Author for correspondence:

Robert Koller

Tel: +49 221 4702927

Email: rkoller@uni-koeln.de

Summary

  • Dead organic matter (OM) is a major source of nitrogen (N) for plants. The majority of plants support N uptake by symbiosis with arbuscular mycorrhizal (AM) fungi. Mineralization of N is regulated by microfauna, in particular, protozoa grazing on bacteria. We hypothesized that AM fungi and protozoa interactively facilitate plant N nutrition from OM.
  • In soil systems consisting of an OM patch and a root compartment, plant N uptake and consequences for plant carbon (C) allocation were investigated using stable isotopes.
  • Protozoa mobilized N by consuming bacteria, and the mobilized N was translocated via AM fungi to the host plant. The presence of protozoa in both the OM and root compartment stimulated photosynthesis and the translocation of C from the host plant via AM fungi into the OM patch. This stimulated microbial activity in the OM patch, plant N uptake from OM and doubled plant growth.
  • The results indicate that protozoa increase plant growth by both mobilization of N from OM and by protozoa–root interactions, resulting in increased C allocation to roots and into the rhizosphere, thereby increasing plant nutrient exploitation. Hence, mycorrhizal plants need to interact with protozoa to fully exploit N resources from OM.

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