Ultrastructural Features of Developing and Mature Basidia and Basidiospores of Schizophyllum commune

Abstract

The ultrastructure of the dikaryotic and diploid basidia of Schizophyllum commune Fries is essentially similar to that described in other fungi. Extracytoplasmic loculi are formed in the basal region of the basidium and adjacent segments of the fertile hypha by imagination and recurvature of the ectoplast. Patches of glycogen granules appear first in basidia at the nonvacuolated, 4-nucleated stage. The glycogen granules become evenly dispersed during vacuolation. After vacuolation the electron-dense hilum is formed centripetally, and a cup-like, parahilar, electron-transparent layer develops between the wall and the ectoplast of the basidiospore. A thin, fragile extension of the wall of the sterigma is present around the base of the basidiospore. It is believed that the drop develops within that portion of the extension of the sterigma wall covering the hilar appendix. It is postulated that the enlargement of the drop contributes to the rupturing of the contiguous surfaces between the sterigma and the spore and to the force of discharge. The fact that the ectoplast, as seen in longitudinal thin sections, is level prior to discharge and convex after discharge suggests that turgor pressure within the basidium also contributes to the force of basidiospore discharge.