Substantial nitrogen acquisition by arbuscular mycorrhizal fungi from organic material has implications for N cycling

TY - JOUR

T1 - Substantial nitrogen acquisition by arbuscular mycorrhizal fungi from organic material has implications for N cycling

AU - Hodge, Angela

AU - Fitter, Alastair H.

PY - 2010

Y1 - 2010

N2 - Arbuscular mycorrhizal (AM) fungi are obligate biotrophs that acquire carbon (C) solely from host plants. AM fungi can proliferate hyphae in, and acquire nitrogen (N) from, organic matter. Although they can transfer some of that N to plants, we tested the hypothesis that organic matter is an important N source for the AM fungi themselves. We grew pairs of plants with and without the AM fungus Glomus hoi in microcosms that allowed only the fungus access to a N-15/C-13-labeled organic patch; in some cases, one plant was shaded to reduce C supply to the fungus. The fungal hyphae proliferated vigorously in the patch, irrespective of shading, and increased plant growth and N content; similar to 3% of plant N came from the patch. The extraradical mycelium of the fungus was N-rich (3-5% N) and up to 31% of fungal N came from the patch, confirming the hypothesis. The fungus acquired N as decomposition products, because hyphae were not C-13-enriched. In a second experiment, hyphae of both G. hoi and Glomus mosseae that exploited an organic material patch were also better able to colonize a new host plant, demonstrating a fungal growth response. These findings show that AM fungi can obtain substantial amounts of N from decomposing organic materials and can enhance their fitness as a result. The large biomass and high N demand of AM fungi means that they represent a global N pool equivalent in magnitude to fine roots and play a substantial and hitherto overlooked role in the nitrogen cycle.

AB - Arbuscular mycorrhizal (AM) fungi are obligate biotrophs that acquire carbon (C) solely from host plants. AM fungi can proliferate hyphae in, and acquire nitrogen (N) from, organic matter. Although they can transfer some of that N to plants, we tested the hypothesis that organic matter is an important N source for the AM fungi themselves. We grew pairs of plants with and without the AM fungus Glomus hoi in microcosms that allowed only the fungus access to a N-15/C-13-labeled organic patch; in some cases, one plant was shaded to reduce C supply to the fungus. The fungal hyphae proliferated vigorously in the patch, irrespective of shading, and increased plant growth and N content; similar to 3% of plant N came from the patch. The extraradical mycelium of the fungus was N-rich (3-5% N) and up to 31% of fungal N came from the patch, confirming the hypothesis. The fungus acquired N as decomposition products, because hyphae were not C-13-enriched. In a second experiment, hyphae of both G. hoi and Glomus mosseae that exploited an organic material patch were also better able to colonize a new host plant, demonstrating a fungal growth response. These findings show that AM fungi can obtain substantial amounts of N from decomposing organic materials and can enhance their fitness as a result. The large biomass and high N demand of AM fungi means that they represent a global N pool equivalent in magnitude to fine roots and play a substantial and hitherto overlooked role in the nitrogen cycle.

KW - nutrient capture

KW - organic patches

KW - stable isotopes

KW - fitness

KW - GLOMUS-INTRARADICES

KW - ROOT PROLIFERATION

KW - PLANT

KW - SOIL

KW - PHOSPHATE

KW - FIELD

KW - CAPTURE

KW - PATCHES

KW - CARBON

KW - HYPHAE

UR - http://www.scopus.com/inward/record.url?scp=77956380625&partnerID=8YFLogxK

U2 - 10.1073/pnas.1005874107

DO - 10.1073/pnas.1005874107

M3 - Article

SN - 0027-8424

VL - 107

SP - 13754

EP - 13759

JO - Proceedings of the National Academy of Sciences of the United States of America

JF - Proceedings of the National Academy of Sciences of the United States of America

IS - 31

ER -