Subcellular trace element distribution in Geosiphon pyriforme

Geosiphon pyriforme is a unique endosymbiotic consortium consisting of a so il dwelling fungus and the cyanobacterium Nostoc punctiforme, At present th is symbiosis becomes very interesting because of its phylogenetic relations hip to the arbuscular mycorrhizal (AM) fungi. Geosiphon pyriforme could be an important model system for these obligate symbiotic fungi, which supply 80-90%; of all land plant species with nutrients, in particular phosphorous and trace elements. Combined PIXE and STIM analyses of the various compart ments of Geosiphon give hints for the matter exchange between the symbiotic partners and their environment and the kind of nutrient storage and acquis ition, in particular related to nitrogen fixation and metabolism. To determ ine the quality of our PINE results we analysed several geological and biol ogical standards over a time period of three years. This led to an overall precision of about 6% and an accuracy of 5-10% for nearly all detectable el ements, In combination with the correction model for the occurring mass los s during the analyses this holds true even for biological targets. (C) 1999 Elsevier Science B.V. All rights reserved.