Mycorrhizal mediated feedbacks influence net carbon gain and nutrient uptake in Andropogon gerardii

Authors

  • R. M. Miller,

    Corresponding author
    1. Environmental Research Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439, USA;
      Author for correspondence: R. M. Miller Tel: +1 630 2523395 Fax: +1 630 2528895 Email: rmmiller@anl.gov
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  • S. P. Miller,

    1. Department of Agronomy, University of Kentucky, N-122 Agricultural Sciences North, Lexington, KY 40506-0091, USA
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  • J. D. Jastrow,

    1. Environmental Research Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439, USA;
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  • C. B. Rivetta

    1. Environmental Research Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439, USA;
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  • This manuscript has been created by the University of Chicago as operator of Argonne National Laboratory under Contract No. W-31-109-ENG-38 with the US Department of Energy. The US government retains for itself, and others acting on its behalf, a paid-up, nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the government.

Author for correspondence: R. M. Miller Tel: +1 630 2523395 Fax: +1 630 2528895 Email: rmmiller@anl.gov

Summary

  • • The carbon sink strength of arbuscular mycorrhizal fungi (AMF) was investigated by comparing the growth dynamics of mycorrhizal and nonmycorrhizal Andropogon gerardii plants over a wide range of equivalent tissue phosphorus : nitrogen (P : N) ratios.
  • • Host growth, apparent photosynthesis (Anet), net C gain (Cn) and P and N uptake were evaluated in sequential harvests of mycorrhizal and nonmycorrhizal A. gerardii plants. Response curves were used to assess the effect of assimilate supply on the mycorrhizal symbiosis in relation to the association of C with N and P.
  • • Mycorrhizal plants had higher Cn than nonmycorrhizal plants at equivalent shoot P : N ratios even though colonization did not affect plant dry mass. The higher Cn in mycorrhizal plants was related to both an increase in specific leaf area and enhanced photosynthesis. The additional carbon gain associated with the mycorrhizal condition was not allocated to root biomass. The Cn in the mycorrhizal plants was positively related to the proportion of active colonization in the roots.
  • • The calculated difference between Cn values in mycorrhizal and nonmycorrhizal plants, Cdiff, appeared to correspond to the sink strength of the AMF and was not an indirect result of enhanced nutrition in mycorrhizal plants.

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