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The Ascus Apex in Lichenized Fungi II. The Rhizocarpon-Type


Honegger, Rosmarie (1980). The Ascus Apex in Lichenized Fungi II. The Rhizocarpon-Type. The Lichenologist, 12(02):157-172.

Abstract

Ascus structure of eight yellow, two white and two brown <jats:italic>Rhizocarpon</jats:italic> species has been investigated by light microscopy. Ultrastructure and function in R. <jats:italic>atroflavescens</jats:italic> subsp. <jats:italic>pulverulentum</jats:italic> and <jats:italic>R. montagnei</jats:italic> were studied in TEM.The <jats:italic>Rhizocarpon</jats:italic>-type ascus clearly differs from all other ascus types observed in the Lecanorales. It is bitunicate, opening with a slight ‘Jack-in-the-box’-mechanism. Its structure and function are related to patellariacean ascus types, but unlike those the ascus wall cytochemistry shows a certain similarity with <jats:italic>Lecanora</jats:italic>- and <jats:italic>Peltigera</jats:italic>-type asci. <jats:italic>Rhizocarpon</jats:italic>-type asci are embedded in a strongly amyloid hymenial gelatine. The nonamyloid ascus wall is surrounded by the strongly amyloid outer layer. The slightly amyloid expansible inner layer (= endoascus) is apically thickened; it shows the banded and pleated ‘accordion-structure’ characteristic of bitunicate asci. Prior to dehiscence, the ascus wall and its outer layer burst. Thereafter the pleatings of the expansible inner layer are stretched, forming the rather short beak which reaches the hymenial surface. During expansion gliding occurs between the expansible inner layer and an outer part of the endoascus, here described as the ‘inner layer’. In a few sections of aldehyde- fixed material of <jats:italic>R. atroflavescens</jats:italic> a small laminated plug was observed in the apex of the endoascus.<jats:italic>Rhizocarpon</jats:italic>-lype asci are considered to be the most archaic in the Lecanorales. This supports a hypothesis that <jats:italic>Rhizocarpon</jats:italic> is a phylogenetically basal group, linking the evolved Lecanorineae, and possibly also the Peltigerineae and Teloschistineae with not yet recognized bitunicate ancestral forms similar to those occurring in the Patellariaceae.

Abstract

Ascus structure of eight yellow, two white and two brown <jats:italic>Rhizocarpon</jats:italic> species has been investigated by light microscopy. Ultrastructure and function in R. <jats:italic>atroflavescens</jats:italic> subsp. <jats:italic>pulverulentum</jats:italic> and <jats:italic>R. montagnei</jats:italic> were studied in TEM.The <jats:italic>Rhizocarpon</jats:italic>-type ascus clearly differs from all other ascus types observed in the Lecanorales. It is bitunicate, opening with a slight ‘Jack-in-the-box’-mechanism. Its structure and function are related to patellariacean ascus types, but unlike those the ascus wall cytochemistry shows a certain similarity with <jats:italic>Lecanora</jats:italic>- and <jats:italic>Peltigera</jats:italic>-type asci. <jats:italic>Rhizocarpon</jats:italic>-type asci are embedded in a strongly amyloid hymenial gelatine. The nonamyloid ascus wall is surrounded by the strongly amyloid outer layer. The slightly amyloid expansible inner layer (= endoascus) is apically thickened; it shows the banded and pleated ‘accordion-structure’ characteristic of bitunicate asci. Prior to dehiscence, the ascus wall and its outer layer burst. Thereafter the pleatings of the expansible inner layer are stretched, forming the rather short beak which reaches the hymenial surface. During expansion gliding occurs between the expansible inner layer and an outer part of the endoascus, here described as the ‘inner layer’. In a few sections of aldehyde- fixed material of <jats:italic>R. atroflavescens</jats:italic> a small laminated plug was observed in the apex of the endoascus.<jats:italic>Rhizocarpon</jats:italic>-lype asci are considered to be the most archaic in the Lecanorales. This supports a hypothesis that <jats:italic>Rhizocarpon</jats:italic> is a phylogenetically basal group, linking the evolved Lecanorineae, and possibly also the Peltigerineae and Teloschistineae with not yet recognized bitunicate ancestral forms similar to those occurring in the Patellariaceae.

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Item Type:Journal Article, refereed, original work
Communities & Collections:National licences > 142-005
Dewey Decimal Classification:Unspecified
Scopus Subject Areas:Life Sciences > Ecology, Evolution, Behavior and Systematics
Language:English
Date:1 June 1980
Deposited On:01 Nov 2018 13:37
Last Modified:31 Jul 2020 02:15
Publisher:Cambridge University Press
ISSN:0024-2829
OA Status:Green
Publisher DOI:https://doi.org/10.1017/s002428298000014x
Related URLs:https://www.swissbib.ch/Search/Results?lookfor=nationallicencecambridge101017S002428298000014X (Library Catalogue)

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