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Bryological and Lichenological Section/ABLS

Schuette, Scott [1], Cargill, Christine [2], Renzaglia, Karen S. [1].

Precocious and Endosporic Spore Germination in Dendroceros crispatus: Taxonomic Implications.

The epiphytic Dendroceros is the only hornwort with precocious, endosporic and multicellular spores. This study examines the ultrastructural changes that accompany spore differentiation in Dendroceros from unicellular through mature multicellular spores. Following meiosis, spore walls are deposited by vesicles and consist of an inner fibrillar intine and a two-layered exine, including a highly convoluted outer layer. Unicellular spores are arranged in tetrahedral tetrads and have distinctly vermiform external spore morphologies with closely spaced distal papillae and prominent trilete marks. Young tetrads fill the available space and spores undergo rapid mitotic divisions while still contained in the capsule. As space constraints are reduced through capsule drying and dehiscence, continued divisions are responsible for spore expansion to more than 30 cells, while concomitantly stretching the convoluted exine and significantly changing the external spore morphology. Mature, released spores are vermiform, however distal papillae are widely spaced and the trilete marks are poorly defined. Additionally, spores proceed from tetrahedral to compressed shapes making distal and proximal orientation difficult to discern. With spore shape, size and morphology as characters traditionally used to determine Dendroceros species, it is crucial to consider age of the sporophyte and stage of spore development when making species determinations.


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1 - Southern Illinois University, Department of Plant Biology, 1125 Lincoln Drive, Carbondale, Illinois, 62901-6509, USA
2 - Centre for Plant Biodiversity Research Centre for Plant, CSIRO Plant Industry, GPO Box 1600, Canberra, Australian Capital Territory, 2601, Australia

Keywords:
hornwort
morphology
spore
ultrastructure.

Presentation Type: Oral Paper
Session: 51-4
Location: 400/Hilton
Date: Wednesday, August 17th, 2005
Time: 2:15 PM
Abstract ID:263


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