Enzyme localization

The importance of ectomycorrhizal fungi in phosphate absorption and storage has prompted several studies related to the presence and localization of phosphatases in isolated mycorrhizal fungi and within ectomycorrhiza.

The research on isolated ectomycorrhizal fungi involves biochemical techniques for extraction and identification of phosphatases (see Ho, 1989), whereas histochemical procedures involving lead precipitation on sections prepared for transmission electron microscopy have been used in some studies of ectomycorrhiza. The discussion on phosphatases will be limited to those involving histochemical procedures. Dexheimer et al. (1986) showed that acid phosphatases were localized along the plasma membranes of Hartig net fungal hyphae and adjacent cortical cells in two host-fungus combinations as long as the hyphae were not senescent. Mantle hyphae also showed this distribution unless they were undergoing autolysis, in which case, like old Hartig net hyphae, acid phosphatase was present throughout the fungal cytoplasm. Some activity of acid phosphatase was also present in the matrix material of the mantle and along the interface between the mantle and the rooting medium.

Lei and Dexheimer (1988), in a study of the localization of ATPase in Pinus sylvestris-Laccaria laccata ectomycorrhiza, showed that this enzyme was located along the plasma membrane of cortical cells, external hyphae, Hartig net hyphae and mantle hyphae. Degenerating cortical cells did not have ATPase activity and neither did the plasma membrane of Hartig net hyphae adjacent to senescing cortical cells.

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