Ultrastructural study and cytochemical investigation, by means of enzyme–gold complexes, of the fungus Ascocalyx abietina

Abstract

The fungus Ascocalyx abietina (Lagerberg.) Schlaepfer-Bernhard, the scleroderris canker agent of conifers, is composed of a regularly septate mycelium, often branched at divergent angles. All fungal cells appear delimited by a thick wall surrounded by a dense fibrillar network. Peculiar ultrastructural characteristics of this fungus were observed, such as irregular nuclei with multishaped blebs and endoplasmic reticulum oriented in definite parallel arrays. Presence of single or multiple endocells was frequently observed. In some instances, gaps were present in the walls of enclosing cells where the cytoplasmic contents had escaped. Amylase, chitinase, β-galactosidase, lipase, and cellulose–gold complexes were used to localize various substances in A. abietina cells. With such complexes N-acetyl-D-glucosamine, β-galactosides, and lipids were detected in the cell walls, while glycogen deposits were found to occur in cytoplasmic electron-transparent bodies. The present work presents the ultrastructural features of A. abietina and adds to some of the cytochemical aspects recently reported.