Storage and secretion processes in the spore of Gigaspora margarita Becker & Hall as revealed by high-pressure freezing and freeze substitution.

Spores of Gigaspora margarita Becker & Hall, an arbuscular mycorrbizal fungus, were cryofixed using big pressure freezing and prepared for transmission electron microscopy by freeze substitution. The cryotechniques improved tbe ultrastructural preservation of tbe spore cytoplasm and revealed storage and secretion processes in tbe germinating spores of G. margarita. The storage structures in the bydrated and/or germinating spores bave been identified as belonging to three different classes: (i) lipid droplets limited by a membrane, (ii) protein-like bodies inside specialized vacuoles, and (ii) glicogen particles. During germ-tube differentiation, an abundant membranous system was observed. It consists of rough ER. tubules and balloon-like Golgi equivalents, which produce vesicles associated with electron-dense granules. Tbe granules seem to be incorporated info the wall. The results suggest that secretion and storage occur in the fungal spore during events comparable to those in yeasts or plant cells.