title: Transfer of13C between paired Douglas-fir seedlings reveals plant kinship effects and uptake of exudates by ectomycorrhizas.
abstract: Processes governing the fixation, partitioning, and mineralization of carbon in soils are under increasing scrutiny as we develop a more comprehensive understanding of global carbon cycling. Here we examined fixation by Douglas-fir seedlings and transfer to associated ectomycorrhizal fungi, soil microbes, and full-sibling or nonsibling neighbouring seedlings. Stable isotope probing with 99%13C-CO2was applied to trace13C-labelled photosynthate throughout plants, fungi, and soil microbes in an experiment designed to assess the effect of relatedness on13C transfer between plant pairs. The fixation and transfer of the13C label to plant, fungal, and soil microbial tissue was examined in biomass and phospholipid fatty acids. After a 6 d chase period, c. 26.8% of the13C remaining in the system was translocated below ground. Enrichment was proportionally greatest in ectomycorrhizal biomass. The presence of mesh barriers (0.5 or 35 μm) between seedlings did not restrict13C transfer. Fungi were the primary recipients of13C-labelled photosynthate throughout the system, representing 60-70% of total13C-enriched phospholipids. Full-sibling pairs exhibited significantly greater13C transfer to recipient roots in two of four Douglas-fir families, representing three- and fourfold increases (+ c. 4 μg excess13C) compared with nonsibling pairs. The existence of a root/mycorrhizal exudation-hyphal uptake pathway was supported.
authors.affiliation: Department of Forest and Conservation Sciences, University of British Columbia, Vancouver, BC, Canada, V6T 1Z4.|School of Biological Sciences, University of Reading, Harborne Building, Whiteknights, Reading, RG6 6AS, UK.
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Pickles
authors.affiliation: Department of Microbiology & Immunology, Life Sciences Institute, University of British Columbia, Vancouver, BC, Canada, V6T 1Z3.
authors.forename: Roland
authors.initials: R
authors.lastname: Wilhelm
authors.affiliation: Department of Forest and Conservation Sciences, University of British Columbia, Vancouver, BC, Canada, V6T 1Z4.
authors.forename: Amanda K
authors.initials: AK
authors.lastname: Asay
authors.affiliation: Department of Microbiology & Immunology, Life Sciences Institute, University of British Columbia, Vancouver, BC, Canada, V6T 1Z3.
authors.forename: Aria S
authors.initials: AS
authors.lastname: Hahn
authors.affiliation: Department of Forest and Conservation Sciences, University of British Columbia, Vancouver, BC, Canada, V6T 1Z4.
authors.forename: Suzanne W
authors.initials: SW
authors.lastname: Simard
authors.affiliation: Department of Microbiology & Immunology, Life Sciences Institute, University of British Columbia, Vancouver, BC, Canada, V6T 1Z3.
authors.forename: William W
authors.initials: WW
authors.lastname: Mohn
mesh_terms: D002244:Carbon / Q000378:metabolism; D002247:Carbon Isotopes / Q000378:metabolism*; D005658:Fungi / Q000378:metabolism; D025301:Hyphae / Q000378:metabolism; D016014:Linear Models; D018519:Meristem / Q000382:microbiology; D038821:Mycorrhizae / Q000378:metabolism*; D010743:Phospholipids / Q000378:metabolism; D010788:Photosynthesis; D053147:Plant Exudates / Q000378:metabolism*; D028224:Pseudotsuga / Q000378:metabolism* / Q000382:microbiology*; D036226:Seedlings / Q000378:metabolism* / Q000382:microbiology*; D012987:Soil / Q000737:chemistry
chemical_list: D002247:Carbon Isotopes; D010743:Phospholipids; D053147:Plant Exudates; D012987:Soil; D002244:Carbon
keywords: carbon (C) allocation; ectomycorrhizas; host relatedness; interior Douglas-fir; phospholipid fatty acid (PLFA); stable-isotope probing