title: Arbuscular mycorrhizal fungi contribute to phosphorus uptake by wheat grown in a phosphorus-fixing soil even in the absence of positive growth responses.
abstract: 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.
authors.affiliation: 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. h.li@adelaide.edu.au
authors.forename: Huiying
authors.initials: H
authors.lastname: Li
authors.forename: Sally E
authors.initials: SE
authors.lastname: Smith
authors.forename: Robert E
authors.initials: RE
authors.lastname: Holloway
authors.forename: Yongguan
authors.initials: Y
authors.lastname: Zhu
authors.forename: F Andrew
authors.initials: FA
authors.lastname: Smith
mesh_terms: D038821:Mycorrhizae / Q000502:physiology*; D010758:Phosphorus / Q000737:chemistry* / Q000378:metabolism*; D010761:Phosphorus Radioisotopes / Q000737:chemistry / Q000378:metabolism; D012987:Soil / Q000032:analysis*; D014908:Triticum / Q000254:growth & development / Q000378:metabolism* / Q000382:microbiology*
chemical_list: D010761:Phosphorus Radioisotopes; D012987:Soil; D010758:Phosphorus