Geosiphon

Geosiphon is a genus of the phylum Glomeromycota, Order Archaeosporales, Family Geosiphonaceae.

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Life cycle

Geosiphon pyriformis is known for being the symbiont of Nostoc. The Geosiphon-Nostoc symbiosis, as by modern definitions, is not a lichen, since it is an intracellular association. Also by functional and evolutionary implications it is more comparable to the arbuscular mycorrhiza symbioses, then to lichens!

The Geosiphon-Nostoc symbiosis is the only known fungal endosymbiosis with cyanobacteria and is characterised by a "siphonal bladder" that is made of a swollen fungal hypha, 0.5-2 mm in size and growing on the soil surface. The upper 2/3 of the "bladder" contains the Nostoc filaments and Nostoc heterocysts, the lower 1/3 is filled with lipid droplets.

Reproduction

The fungal spores are 250 micrometres in diameter, formed at the end of one hypha, or intercalarly (within a hyphae) and resemble those of members of the Glomeromycota.

Somatic structure

Geosiphon has a specialised bladder used to harbour cyanobacteria. Geosiphon pyriformis is not known to form arbuscular mycorrhiza.

References

http://www.geosiphon.de http://www.amf-phylogeny.com

• C.J. Alexopolous, Charles W. Mims, M. Blackwell, Introductory Mycology, 4^th ed. (John Wiley and Sons, Hoboken NJ, 2004) ISBN 0-471-52229-5