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

The influence of three organic compounds and bakers' dry yeast on growth of external mycelium and phosphorus uptake of the arbuscular mycorrhizal fung us Glomus intraradices Schenck & Smith (BEG 87) was examined. Two experimen ts 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 cellul ose. 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 oth er than the arbuscular mycorrhizal fungus were measured by fatty acid signa tures, and radioactive P-33 labelling of the root-free soil was used to det ermine arbuscular mycorrhizal hyphal phosphorus uptake, In general, hyphal growth of G. intraradices was enhanced by yeast and bovine serum albumin, w hereas the carbon sources, starch and cellulose, depressed fungal growth. B y analysing the fatty acid 16:1 omega 5 from phospholipids (indicating myce lium) and neutral lipids (indicating storage structures) it was shown that increased fungal growth due to S-east was mainly in vegetative hyphae and l ess 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 arbu scular mycorrhizal hyphal growth and phosphorus uptake.