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Abstract
The ultrastructure of cells of the sclerotia and aerial mycelium of Sclerotium rolfsii Sacc. was studied by electron microscopy. A mature sclerotium of S. rolfsii contains several types of differentiated cells. The thick-walled rind cells which comprise the sclerotial envelope are empty. The underlying cortex cells have thinner walls and contain many vesicles full of reserve materials which appear dark after treatment with osmium tetroxide. Although less reactive to osmium tetroxide, the cells between the cortex and medulla are also rich in reserve materials, some of which are membrane-bound. The inner layer (medulla) is composed of cells with extremely thick walls, of thinner-walled cells full of reserve materials and of empty cells. The walls of the hyphal cells are significantly thinner, and less optically dense than the walls of any of the sclerotial cells. Hyphal cells contain more ribosomes and mitochondria than sclerotial cells.
It seems that the resistance of sclerotia to biological degradation depends upon the melanin-rich rind as well as the wall structure and organization of cells comprising the inner layers of the sclerotium.
- Accepted:
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