Arbuscular mycorrhizal fungi contribute to phosphorus uptake by wheat grown in a phosphorus-fixing soil even in the absence of positive growth responses

Authors

  • Huiying Li,

    1. Centre for Soil–Plant Interactions, Soil and Land Systems, School of Earth and Environmental Sciences, Waite Campus, DP636, The University of Adelaide, South Australia, 5005, Australia;
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  • Sally E. Smith,

    1. Centre for Soil–Plant Interactions, Soil and Land Systems, School of Earth and Environmental Sciences, Waite Campus, DP636, The University of Adelaide, South Australia, 5005, Australia;
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  • Robert E. Holloway,

    1. Centre for Soil–Plant Interactions, Soil and Land Systems, School of Earth and Environmental Sciences, Waite Campus, DP636, The University of Adelaide, South Australia, 5005, Australia;
    2. Minnipa Agricultural Centre, South Australian Research and Development Institute, PO Box 31, Minnipa, South Australia, 5654, Australia;
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  • Yongguan Zhu,

    1. Centre for Soil–Plant Interactions, Soil and Land Systems, School of Earth and Environmental Sciences, Waite Campus, DP636, The University of Adelaide, South Australia, 5005, Australia;
    2. Research Centre for Eco-environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
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  • F. Andrew Smith

    1. Centre for Soil–Plant Interactions, Soil and Land Systems, School of Earth and Environmental Sciences, Waite Campus, DP636, The University of Adelaide, South Australia, 5005, Australia;
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Author for correspondence: Huiying Li Tel: +61 (8) 83036787 Fax: +61 (8) 83036511 Email: h.li@adelaide.edu.au

Summary

  • • We used 32P to quantify the contribution of an arbuscular mycorrhizal (AM) fungus (Glomus intraradices) to phosphorus (P) uptake by wheat (Triticum aestivum), grown in compartmented pots. The soil was from a major cereal-growing area, the Eyre Peninsula, South Australia; it was highly calcareous and P-fixing. Fertilizer P was added to soil at 20 mg kg−1, as solid or liquid. Two extraction methods were used to estimate plant-available P.
  • • Fungal colonization was well established at harvest (36 d). Application of P decreased both colonization and hyphal length density in soil, with small differences between different P fertilizers.
  • • Plants showed large positive responses in terms of growth or total P uptake to all P additions, and showed no positive (or even negative) responses to AM colonization, regardless of P application.
  • • 32P was detected only in AM plants, and we calculated that over 50% of P uptake by plants was absorbed via AM fungi, even when P was added. The results add to the growing body of knowledge that ‘nonresponsive’ AM plants have a functional AM pathway for P transfer to the plant; it should not be ignored in breeding plants for root traits designed to improve P uptake.

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