Fine structure of imbibed sclerotial cells of Claviceps purpurea (Fr.) Tul revealed by freeze-etching.

The fine structure of the cortex of the natural sclerotium of Claviceps purpurea was studied. The cell wall of sclerotial cells is thickened due to overproduction of the fibrillar component of the wall. The intracellular spaces of the cortex tissue form a continuous system which is apparently instrumental in mediating communication between the growing sclerotium and the external milieu. The cytoplasmic membrane of imbibed sclerotial cells carriers abundant signs of secretory activity. Secretion vesicles, the content of which is discharged into external space, apparently contain exo 1,3-glucanase. Cytoplasmic vesicles migrating toward the plugged pores of the thickened septa apparently involve hydrolase secretion too. Spherosomes with lipid content are a predominant component of the cytoplasm of sclerotial cells. The activity of the membrane systems of imbibed cells indicates that the mobilization of lipids sets in only after activation of the hydrolases. Findings of phagocytosis of lipid granules by vacuoles are relatively frequent so that lipolysis might proceed in the vacuoles. Alkaloids could not be detected with the aid of freeze-etching.