CHANGES IN THE WALL POTENTIAL OF SCUTELLOSPORA-CALOSPORA ASSOCIATED WITH COLONIZATION OF ALLIUM-PORRUM ROOTS ARE NOT ACCOMPANIED BY EQUIVALENT CHANGES IN THE HOST

Cell wall electrical potentials were recorded from external hyphae, ap pressoria, and associated hyphae of the vesicular-arbuscular (VA) myco rrhizal fungus Scutellospora calospora (Nicolson & Gerdemann) Walker & Sanders colonizing leek (Allium porrum L.) roots. As colonization pro gressed the hyphal walls became more polarized with similar values to the walls of the leek root. These changes, which may reflect changes i n fungal wall composition, have important implications for nutrient up take by the fungus. There were no differences in wall or intracellular potentials between leek roots colonized by either S. calospora or Glo mus sp. (''City Beach'') and non-mycorrhizal roots. These results are further evidence of the close compatibility between roots and VA mycor rhizal fungi.