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Effects of various organic compounds on growth and phosphorus uptake of an arbuscular mycorrhizal fungus

Published online by Cambridge University Press:  01 March 1999

SABINE RAVNSKOV
Affiliation:
Plant Biology and Biogeochemistry Department, Risø National Laboratory, DK-4000 Roskilde, Denmark
JOHN LARSEN
Affiliation:
Department of Microbial Ecology, Ecology Building, Lund University, S-223 62 Lund, Sweden Current address: Department of Crop Protection, Danish Institute of Agricultural Sciences, Flakkebjerg DK-4200 Slagelse, Denmark (e-mail sabine.ravnskov@risoe.dk)
PÅL AXEL OLSSON
Affiliation:
Department of Microbial Ecology, Ecology Building, Lund University, S-223 62 Lund, Sweden
IVER JAKOBSEN
Affiliation:
Plant Biology and Biogeochemistry Department, Risø National Laboratory, DK-4000 Roskilde, Denmark
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Abstract

The influence of three organic compounds and bakers' dry yeast on growth of external mycelium and phosphorus uptake of the arbuscular mycorrhizal fungus Glomus intraradices Schenck & Smith (BEG 87) was examined. Two experiments were carried out in compartmentalized growth systems with root-free sand or soil compartments. The sand and soil in the root-free compartments were left untreated or uniformly mixed with one of the following substrates (0.5 mg g−1 soil): bakers' dry yeast, bovine serum albumin, starch or cellulose. Effects of the organic substrates on biomass and hyphal length density of the arbuscular mycorrhizal fungus were examined by using specific fatty acid signatures in combination with direct microscopy. Micro-organisms other than the arbuscular mycorrhizal fungus were measured by fatty acid signatures, and radioactive 33P labelling of the root-free soil was used to determine arbuscular mycorrhizal hyphal phosphorus uptake. In general, hyphal growth of G. intraradices was enhanced by yeast and bovine serum albumin, whereas the carbon sources, starch and cellulose, depressed fungal growth. By analysing the fatty acid 16[ratio ]1ω5 from phospholipids (indicating mycelium) and neutral lipids (indicating storage structures) it was shown that increased fungal growth due to yeast was mainly in vegetative hyphae and less in storage structures. Arbuscular mycorrhizal hyphal phosphorus uptake was decreased by cellulose, but unaffected by the other substrates compared with the control. This means that both growth and phosphorus transport by the arbuscular mycorrhizal fungus were decreased under cellulose treatment. However, the composition of the microbial community varied under different substrate conditions indicating a possible interactive component with arbuscular mycorrhizal hyphal growth and phosphorus uptake.

Type
Research Article
Copyright
© Trustees of New Phytologist 1999

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