Changes in the wall potential ofScutellospora calosporaassociated with colonization ofAllium porrumroots are not accompanied by equivalent changes in the host

Cell wall electrical potentials were recorded from external hyphae, appressoria, and associated hyphae of the vesicular-arbuscular (VA) mycorrhizal fungus Scutellospora calospora (Nicolson & Gerdemann) Walker & Sanders colonizing leek (Allium porrum L.) roots. As colonization progressed the hyphal walls became more polarized with similar values to the walls of the leek root. These changes, which may reflect changes in fungal wall composition, have important implications for nutrient uptake by the fungus. There were no differences in wall or intracellular potentials between leek roots colonized by either S. calospora orGlomus sp. ("City Beach") and non-mycorrhizal roots. These results are further evidence of the close compatibility between roots and VA mycorrhizal fungi. Key words: vesicular-arbuscular mycorrhiza, cell wall, electrical potential difference, leek, Allium porrum, Scutellospora calospora.