The fine structure and selected histochemistry of ungerminated basidiospores ofAgrocybe acericola

Abstract

The basidiospore wall of Agrocybe acericola is composed of two distinct layers that are continuous around the spores. At the germ pore, the outer wall is very thin and the inner wall becomes thicker. The plasma membrane is appressed to the inner wall and lacks distinct invaginations. The protoplasm is densely packed with ribosomes. Spores contain very little lipid distributed at each end. Mitochondria are well defined and distributed throughout the cytoplasm. Spores are binucleate, with the two nuclei lying on a line nearly perpendicular to the long axis of the cell. Various sizes of single membrane-bound vacuoles are widely distributed in the cytoplasm. These vacuoles were shown to contain acid phosphatase, indicating lysosomal activity. Microbody-like organelles are observed, which are probably glyoxysomes, since assays of malate synthase, a marker enzyme of the glyoxylate cycle, are positive. Keywords: Agrocybe, spore wall ultrastructure, basidiospore ultrastructure, glyoxylate cycle, malate synthase, acid phosphatase.