A morphological study of the mycorrhiza of Entoloma clypeatum f. hybridum on Rosa multiflora

Mycorrhizas of Entoloma clypeatum f. hybridum on Rosa multiflora in the field in Japan were studied by stereo, light and electron microscopy. In most mycorrhizas, the root cap, meristem, and apical region of the cortex disappeared, but in a few mycorrhizas, these tissues remained. Fungal hyphae of the mycorrhizas invaded root tissues and branched palmately. Hyphae in contact with cortical cells were larger than those far from the root cells and contained many mitochondria, cisternae of endoplasmic reticulum and transitional vesicles. Invading hyphae were undulate in the apical part of the mycorrhiza, and some of them lacked distinct organelles. Electron-dense granules accumulated in the root cells adjacent to the fungal hyphae. Both the remnants of the plant cells and the fungal hyphae were included in the amorphous materials on the tip of the stele. These observations suggest the destructive infection by fungal hyphae of the root cells and their collapse near the tip of the stele.