ULTRASTRUCTURAL ASPECTS OF ENDOMYCORRHIZAS IN THE ERICACEAE II. HOST‐ENDOPHYTE RELATIONSHIPS IN VACCINIUM MYRTILLUS L.

The endomycorrhizal infection in Vaccinium myrtillus is limited to the cortical cells of the fine hair roots; the fungi responsible have simple septa with associated Woronin bodies (Ascomycetes). Hyphae penetrating into cells are surrounded by a layer of inner host wall material which diminishes with intracellular development of the fungus. In living cells hyphae are separated from host cytoplasm by continuous host plasmalemma and there is no evidence of their lysis or digestion by the plant cell. This biotrophic relationship (living host cell and fungus) appears to predominate in late summer and autumn when new root formation and mycorrhizal infection are most important. During other periods of the year living or dead fungus in moribund host cells seem to be the most common situation.