Scanning Electron Microscopy of the Contact Site of Conidia and Trichogynes in Cladonia Furcata

Abstract

Abstract:The contact sites of pycnidia and the terminal cells of trichogynes in Cladonia furcata were investigated using either freshly fixed material, or ascomatal primordia and pycnidia from which the gelatinous material either on the primordial surface, or in the pycnidial cavity, had been removed. The sickle-shaped conidia fused, tip first, with the cell wall of trichogynes. Circular holes of about the diameter of the conidia found in the cell walls of trichogynes arise from enzymatic degradation of the wall material by fusing conidia. As the conidia appear to stick on any gelatinous surface material of the thallus the adhesion process is presumed to be unspecific.

Population genetics in the homothallic lichen-forming ascomyceteXanthoria parietina

“…Pycnidia as potential donors of spermatia are present and ascogonia are easy to find within and slightly below the algal layer of submarginal thallus areas (Janex-Favre & Ghaleb 1986), but no trichogynes have so far been detected with light or electron microscopy techniques (R. Honegger, unpublished data). Therefore we conclude that spermatization, a common and widespread mode of dikaryon formation in lichen-forming ascomycetes (Honegger 1984; Honegger & Scherrer 2008), is not the mode of dikaryotization in X. parietina .…”

Myco‐photobiontal selection in a Mediterranean cryptogam community with Fulgensia fulgida

“…The fact that only one ITS-sequence has been found in apothecia of one and the same thallus could be explained by homothallism, which means a fertilisation of trichogynes with pycnospores (which are bacilliform and could serve as spermatia) from the same thallus or cytogamy. Pycnospores have already been interpreted as spermatia, for example by Poelt (1986), amongst others referring to observations made by Honegger (1984) on fusions of pycnospores and trichogynes in Cladonia furcata (Hudson) Schrader. Pycnidia and apothecia were observed on one and the same thallus.…”

Characterisation of the mating-type locus in the genus Xanthoria (lichen-forming ascomycetes, Lecanoromycetes)

“…Spermatization was assumed to be the mode of dikaryon formation in the numerous species in which microconidia have been observed adhering to trichogynes. Microconidia adhering tip Wrst and leaving a hole in the trichogyne wall were found in Cladonia furcata (Honegger, 1984b), but nuclear migration from microconidia to ascogonia has never been documented. The invariably tiny pycnidal microconidia of lichen-forming ascomycetes contain no mitochondria, as concluded from TEM micrographs, fail to germinate and may thus be functionless relics in a large number of lichen species which produce no ascomata and disperse by means of vegetative symbiotic propagules (Honegger, 1984a).…”