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Appl. Environ. Microbiol., Sep 1997, 3531-3538, Vol 63, No. 9
PA Olsson, E Baath and I Jakobsen
The distribution of an arbuscular mycorrhizal (AM) fungus between soil and
roots, and between mycelial and storage structures, was studied by use of
the fatty acid signature 16:1(omega)5. Increasing the soil phosphorus level
resulted in a decrease in the level of the fatty acid 16:1(omega)5 in the
soil and roots. A similar decrease was detected by microscopic measurements
of root colonization and of the length of AM fungal hyphae in the soil. The
fatty acid 16:1(omega)5 was estimated from two types of lipids,
phospholipids and neutral lipids, which mainly represent membrane lipids
and storage lipids, respectively. The numbers of spores of the AM fungus
formed in the soil correlated most closely with neutral lipid fatty acid
16:1(omega)5, whereas the hyphal length in the soil correlated most closely
with phospholipid fatty acid 16:1(omega)5. The fungal neutral
lipid/phospholipid ratio in the extraradical mycelium was positively
correlated with the level of root infection and thus decreased with
increasing applications of P. The neutral lipid/phospholipid ratio
indicated that at high P levels, less carbon was allocated to storage
structures. At all levels of P applied, the major part of the AM fungus was
found to be present outside the roots, as estimated from phospholipid fatty
acid 16:1(omega)5. The ratio of extraradical biomass/intraradical biomass
was not affected by the application of P, except for a decrease at the
highest level of P applied.
Copyright © 1997, American Society for Microbiology
Phosphorus Effects on the Mycelium and Storage Structures of an Arbuscular Mycorrhizal Fungus as Studied in the Soil and Roots by Analysis of Fatty Acid Signatures
Department of Microbial Ecology, Ecology Building, Lund University, S-223 62 Lund, Sweden, and Plant Biology and Biogeochemistry Department, Riso National Laboratory, DK-4000 Roskilde, Denmark
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