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Abstract Detail

MSA - Ecology/Pathology

Lekberg, Ylva [1], Olsson, Pâl Axel [2], Kjoller, Rasmus [1], Michelsen, Anders [1], Rosendahl, Søren [1].

Feast, famine and finding a niche – how seasonal carbon allocation and fungal life history strategies affect biomass and community composition of arbuscular mycorrhizal (AM) fungi.

In nature, plants are linked by multiple AM fungi in complex networks, and molecular identification has revealed a high diversity of previously unknown fungi. However, in-situ symbiotic function, and factors that determine fungal community assemblage are little known. We combined 13CO2 pulse labeling of plants, AM fungal signature lipid analyses, and molecular identification in a Danish grassland to determine if carbon (C) allocation from plants to fungi differ seasonally, how potential differences influence fungal biomass, and whether fungal community composition change concomitantly.
The perennial plant Hypocheris radicata was photosynthetically active throughout the year, but C-assimilation was significantly reduced in February compared with July and October. This resulted in significantly lower 13C concentration in the AM fungal specific neutral lipid 16:1ω5, as well as overall lipid concentration, in roots up to one week after pulse labeling, suggesting that the fungal C-status and plant C-assimilation is tightly linked and dynamic. Contrary, the phospholipid fraction of 16:1ω5, which measures internal fungal membranes, remained constant over the year, and this was supported by non-significant changes in mycorrhizal colonization. Thus, while mycorrhizal structures persisted over the winter, they appeared to have possessed few C-reserves.
There was no significant seasonal shift in AM fungal community composition in H. radicata roots, but a trend toward more sporulating taxa after the summer drought. The dominant taxa are uncultured and display many characteristics associated with K-strategists as they form large mycelia, sporulate rarely and are sensitive to disturbance. Fungi possessing more r-selected traits, such as Glomus mosseae, were present but in low abundance and almost exclusively found associated with the poorly colonized Dianthus deltoids. No arbuscules were observed in those roots, and whether the fungus provides any benefit or is simply taking refuge in this plant awaiting a disturbance event is unclear but is currently under investigation.

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1 - Copenhagen University, Biology, Øster Farimagsgade 2D, Copenhagen, 1353, Denmark
2 - Lund University, Ecology, Ecology Building , Lund, 22362, Sweden

arbuscular mycorrhiza
Carbon allocation
Signature lipid analyses
Community composition
Undisturbed grassland.

Presentation Type: Oral Paper:Papers for Topics
Session: 18
Location: Cottonwood A/Snowbird Center
Date: Monday, July 27th, 2009
Time: 11:00 AM
Number: 18004
Abstract ID:543