Resolving the 'nitrogen paradox' of arbuscular mycorrhizas: fertilization with organic matter brings considerable benefits for plant nutrition and growth.
Arbuscular mycorrhizal fungi (AMF) can transfer nitrogen (N) to host plants, but the ecological relevance is debated, as total plant N and biomass do not generally increase. The extent to which the symbiosis is mutually beneficial is thought to rely on the stoichiometry of N, phosphorus (P) and carbon (C) availability. While inorganic N fertilization has been shown to elicit strong mutualism, characterized by improved plant and fungal growth and mineral nutrition, similar responses following organic N addition are lacking. Using a compartmented microcosm experiment, we determined the significance to a mycorrhizal plant of placing a (15) N-labelled, nitrogen-rich patch of organic matter in a compartment to which only AMF hyphae had access. Control microcosms denied AMF hyphal access to the patch compartment. When permitted access to the patch compartment, the fungus proliferated extensively in the patch and transferred substantial quantities of N to the plant. Moreover, our data demonstrate that allowing hyphal access to an organic matter patch enhanced total plant N and P contents, with a simultaneous and substantial increase in plant biomass. Furthermore, we demonstrate that organic matter fertilization of arbuscular mycorrhizal plants can foster a mutually beneficial symbiosis based on nitrogen transfer, a phenomenon previously thought irrelevant.
Department of Biology, University of York, Wentworth Way, York, YO10 5DD, UK.|Department of Animal and Plant Sciences, University of Sheffield, Western Bank, Sheffield, S10 2TN, UK.
Tom J
0000-0002-4481-0924
TJ
Thirkell
Department of Animal and Plant Sciences, University of Sheffield, Western Bank, Sheffield, S10 2TN, UK.
Duncan D
DD
Cameron
Department of Biology, University of York, Wentworth Way, York, YO10 5DD, UK.
Angela
A
Hodge
D002708:Chlorella; D005308:Fertilizers; D038821:Mycorrhizae / Q000378:metabolism*; D009587:Nitrogen Isotopes / Q000378:metabolism*; D010943:Plantago / Q000254:growth & development / Q000378:metabolism*
D005308:Fertilizers; D009587:Nitrogen Isotopes
arbuscular mycorrhiza; growth; nitrogen; nitrogen paradox; organic matter; symbiosis