Electron Microscope Studies of Lichen Reproductive Structures in Physcia aipolia

Abstract

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The Ascus Apex in Lichenized Fungi I. The Lecanora-, Peltigera- And Teloschistes-Types

“…In Physcia, as well as in other Lecanorales, it can be observed that during a drought period the asci do not manage to release their spores. Some of the spores may begin to germinate in the ascus, as has been described by Rudolph and Giesy (1968), but then both the germinated and ungerminated spores shrink and degenerate. The apical dome of the ascus first shows a lamellate structure (Plate 4C) due to a confluence of the granular electron-dense inclusions.…”

“…The ascus wall is surrounded by an outer layer ('fuzzy coat') identical to the amyloid coat observed in LM. Inside the ascus wall an amyloid dome is formed (Plate 1B-C); this consists, as described by Rudolph and Giesy (1968), of an electron-transparent matrix with granular electron-dense inclusions. These inclusions seem to be responsible for the positive reaction of the dome to iodine.…”

“…As many of the structures mentioned are at the limits of resolution of light microscopy (LM), transmission electron microscope (TEM) studies are needed. Only one previous paper has described the fine structure of a lecanoralean ascus using TEM (Rudolph and Giesy, 1968). In the present study a member of each phylogenetic stage of the 'type bitunique-archaeasce' proposed by Letrouit-Galinou (1973) has been investigated by both LM and TEM.…”

“…All these authors observed a conspicuous amyloid dome at the ascus apex and dehiscence with a rostrum. Rudolph and Giesy (1968) were the first and so far the only workers to make a TEM investigation of a lecanoralean ascus. They observed that in the ascus apex of Physcia aipolia there was an apical thickening consisting of an electron-transparent matrix with electron-dense inclusions.…”

Ultrastructural Modifications in Lichens Induced by Environmental Humidity

“…Jacobs and Ahmadjian (1973) pointed out that the behaviour of pyrenoglobuli under different environmental conditions remained obscure. Dampness seemed to increase the number of globuli (Rudolph and Giesy, 1966;Peveling, 1969) except in one case (Brown and Wilson, 1968), and short-term desiccation was found to reduce their amount (Peveling, 1968) without detectable damage to the thylakoids. Other ultrastructural changes of the phycobiont that occur under dry conditions have been reported by Peveling and Galun (1976).…”