title: Carbon and nitrogen supply to the underground orchid, Rhizanthella gardneri.
abstract: *Rhizanthella gardneri is a rare and fully subterranean orchid that is presumably obligately mycoheterotrophic. R. gardneri is thought to be linked via a common mycorrhizal fungus to co-occurring autotrophic shrubs, but there is no experimental evidence to support this supposition. *We used compartmentalized microcosms to investigate the R. gardneri tripartite relationship. (13)CO(2) was applied to foliage of Melaleuca scalena plants and [(13)C-(15)N]glycine was fed to the common mycorrhizal fungus, and both sources traced to R. gardneri plants. *In our microcosm trial, up to 5% of carbon (C) fed as (13)CO(2) to the autotrophic shrub was transferred to R. gardneri. R. gardneri also readily acquired soil C and nitrogen (N), where up to 6.2% of C and 22.5% of N fed as labelled glycine to soil was transferred via the fungus to R. gardneri after 240 h. *Our study confirms that R. gardneri is mycoheterotrophic and acquires nutrients via mycorrhizal fungus connections from an ectomycorrhizal autotrophic shrub and directly from the soil via the same fungus. This connection with a specific fungus is key to explaining why R. gardneri occurs exclusively under certain Melaleuca species at a very limited number of sites in Western Australia.
authors.affiliation: School of Plant Biology M090, University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia.|Present address: University of British Columbia, 3333 University Way, Kelowna, BC V1V1V7, Canada.
authors.forename: Jeremy J
authors.initials: JJ
authors.lastname: Bougoure
authors.affiliation: School of Plant Biology M090, University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia.
authors.forename: Mark C
authors.initials: MC
authors.lastname: Brundrett
authors.affiliation: School of Plant Biology M090, University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia.
authors.forename: Pauline F
authors.initials: PF
authors.lastname: Grierson
mesh_terms: D002244:Carbon / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism; D002247:Carbon Isotopes; D017753:Ecosystem; D018525:Germination; D005998:Glycine / Q000378:metabolism; D007553:Isotope Labeling; D031650:Melaleuca / Q000378:metabolism / Q000382:microbiology; D038821:Mycorrhizae / Q000502:physiology; D009584:Nitrogen / Q000378:metabolism*; D009587:Nitrogen Isotopes; D029595:Orchidaceae / Q000378:metabolism* / Q000382:microbiology
chemical_list: D002247:Carbon Isotopes; D009587:Nitrogen Isotopes; D002245:Carbon Dioxide; D002244:Carbon; D009584:Nitrogen; D005998:Glycine