Fine Structure of Mycota. 7. Observations on Septa of Ascomycetes and Basidiomycetes

Abstract

Moore, R. T., and J. H. McAlear. (Cornell U., Ithaca, N. Y.) Fine structure of mycota. 7. Observations on septa of Ascomycetes and Basidiomycetes. Amer. Jour. Bot. 49(1): 86–94. Illus. 1962.—Electron microscopy of 13 carpomycete species (5 Ascomycetes, 5 Basidiomycetes, and 3 Deuteromycetes) presents evidence that suggests there is an Ascomycete‐ and a Basidiomycete‐type septum. The observed Ascomycete septa taper slightly or not at all toward a simple, clear‐channel, central pore, while the observed Basidiomycete septa flare sharply and broadly at the center to produce what is termed a dolipore septum. On each side of this septum is a double membrane structure that is crescent‐shaped in section. This is given the name parenthesome. These dolipore‐parenthesome septa were found to be characteristic of basidiocarpic, dikaryotic, hyphae. Interpretative drawings of both types of septa are presented. From these and the micrographs, it is not difficult to see how materials, including nuclei, could pass through the Ascomycete‐type septum, but it would appear that the modifications of the Basidiomycete‐type septum while maintaining cytoplasmic continuity would prohibit nuclear migration in dikaryotic hyphae. It is postulated that as the plant and animal phylogenetic lines have developed actual diploidism, the terminal group of the fungi may have achieved functional diploidism. Of the 3 species of Deuteromycetes examined, 2, Aspergillus variecolor and Stilbum zacalloxanthum, have typical Ascomycete‐type septa; the third, QM 7739, has Basidiomycete‐type septa. This fungus is a species of Sclerotium, but the present confusion and lack of definitive information regarding the taxonomy, genetics, and perfect stage of this genus prohibit the enlarging at present on the possible significance of this observation.

Septal Sealing in the Basidiomycete Coriolus versicolor

“…It suggests that the response to damage is a two stage process. The first stage involves the rapid formation of electron-dense pore plugs, similar in structure to those described by other workers (Moore & McAlear, 1962;Bracker & Butler, 1963;Koltin & Flexer, 1969 . These serve to prevent extensive loss of cytoplasm.…”

Gut passage times in Gammarus pulex (Crustacea, Amphipoda) and aspects of summer feeding in a stony stream

“…It was observed that extraction by the animal could be made through ostensibly intact cross walls of the hyphae . These cross walls in fact probably have the single central pore, about 0 .05 µm across, which is typical in the Ascomycetes and which connects the plasma membrane from cell to cell when the hyphae are viable (Moore & McAlear 1962) . Presumably, when the fungus translocates from a food source to an extending and then sporing hypha, as it will do when growing on leaves in water, this plasma membrane will allow large molecules to pass through .…”

Structures ofSclerotinia SclerotiorumAscocarp and its Septal Pore Ultrastructure

“…DISCUSSION Systematic and phylogenetic problems concerning the Eumycetes have been discussed in countless papers. Besides macroscopical or microscopical characteristics, also ultrastructural and biochemical details are considered very important (MooRE and McALEAR 1962;BRACKER 1967;MooRE 1971MooRE , 1978PATTON and MARCHANT 1978;KHAN and KIMBROUGH 1982).…”