Rapid turnover of hyphae of mycorrhizal fungi determined by AMS microanalysis of 14C.
Processes in the soil remain among the least well-characterized components of the carbon cycle. Arbuscular mycorrhizal (AM) fungi are ubiquitous root symbionts in many terrestrial ecosystems and account for a large fraction of photosynthate in a wide range of ecosystems; they therefore play a key role in the terrestrial carbon cycle. A large part of the fungal mycelium is outside the root (the extraradical mycelium, ERM) and, because of the dispersed growth pattern and the small diameter of the hyphae (<5 micrometers), exceptionally difficult to study quantitatively. Critically, the longevity of these fine hyphae has never been measured, although it is assumed to be short. To quantify carbon turnover in these hyphae, we exposed mycorrhizal plants to fossil ("carbon-14-dead") carbon dioxide and collected samples of ERM hyphae (up to 116 micrograms) over the following 29 days. Analyses of their carbon-14 content by accelerator mass spectrometry (AMS) showed that most ERM hyphae of AM fungi live, on average, 5 to 6 days. This high turnover rate reveals a large and rapid mycorrhizal pathway of carbon in the soil carbon cycle.
Staddon
Philip L
PL
Department of Biology, University of York, Post Office Box 373, York YO10 5YW, UK. philip.louis.staddon@risoe.dk
Ramsey
Christopher Bronk
CB
Ostle
Nick
N
Ineson
Philip
P
Fitter
Alastair H
AH
D002244:Carbon / Q000378:metabolism; D002250:Carbon Radioisotopes; D005658:Fungi / Q000254:growth & development / Q000378:metabolism*; D025301:Hyphae / Q000254:growth & development / Q000378:metabolism*; D038821:Mycorrhizae / Q000254:growth & development / Q000378:metabolism*; D018517:Plant Roots / Q000382:microbiology; D010943:Plantago / Q000382:microbiology*; D012988:Soil Microbiology
D002250:Carbon Radioisotopes; D002244:Carbon