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

- Link: https://rd2.co.nz/substantial-nitrogen-acquisition-by-arbuscular-mycorrhizal-fungi-from-organic-material-has-implications-for-n-cycling/
- Published: 2018-08-06T05:13:43+00:00
- Author: Molly Callaghan

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 15N/13C-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; ∼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 13C-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.
 Angela Hodge and Alastair H. Fitter PNAS August 3, 2010. 107 (31)
13754-13759; https://doi.org/10.1073/pnas.1005874107 Edited by Sandra M. Díaz, Instituto
Multidisciplinario de Biologia Vegetal, Cordoba, Argentina, and approved June 9,
2010 (received for review April 28, 2010)