This study investigated the status of dark septate (DS) fungi in Antarctic plant and soil communities, with the aim of determining the abundance of DS fungi in plant roots and rhizoids, their taxonomic affinities and their symbiotic status. Abundances of fungal hyphae were recorded in roots and rhizoids, and fungi were isolated and identified. Sequencing of ITS (internal transcribed spacer) regions of rDNA indicated that some isolates share taxonomic affinities with fungi of known symbiotic status. Synthesis experiments assessed the effects of DS fungal isolates, including H. ericae, on the growth and nutrient balance of their host plants. Seeds of Deschampsia antarctica and Colobanthus quitensis were collected for use in ecophysiological experiments.