VESICULAR-ARBUSCULAR MYCORRHIZA OF CALAMAGROSTIS-VILLOSA SUPPLIED WITH ORGANIC AND INORGANIC PHOSPHORUS

Plants of Calamagrostis villosa were cultivated in nutrient solution a lone or in association with a vesicular-arbuscular mycorrhizal (VAM) f ungus Glomus etunicatum. They were supplied with two levels of inorgan ic phosphate (P-i; 0.1 or 1 mM) and with or without organic phosphate (dinatriumphenylphosphate, P-o; 1 mM). Depression of growth and enhanc ement of root respiration of mycorrhizal plants in comparison with non -mycorrhizal plants were observed after 12 weeks of cultivation in a g rowth cabinet. Root colonization was not influenced by the higher phos phorus availability in contrast to the extraradical mycelium (ERM). Th e lengths of ERM hyphae both attached to the root surface and in the s ubstrate were decreased substantially by higher phosphorus supply, irr espectively of its form.