A Reassessment of Polyphosphate Granule Composition in the Ectomycorrhizal Fungus Pisolithus tinctorius

Abstract

Comparison of the elemental composition of freeze-substituted and conventionally fixed phosphorus-containing granules of the ectomycorrhizal fungus Pisolithus tinctorius (Pers.) Coker & Couch, using energy dispersive X-ray microanalysis, shows that the cation composition is altered appreciably by the method of specimen preparation. Following conventional chemical fixation, the major cation detected in the granules together with phosphorus was calcium, while freeze-substituted granules most frequently contained phosphorus, potassium and sodium. We conclude that chemical fixation causes serious loss or redistribution of ions. The occurrence of monovalent cations in polyphosphate granules has not previously been demonstrated for mycorrhizal fungi and their presence should be considered in determining the role of the granules in mycorrhizas.