Pyrenomycetes
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Pyrenomycetes
(pī′rē·nō·mī′sēd′ēz)
(mycology) The largest class in the subdivision Ascomycotina, distinguished by a single-walled ascus and the coiled branches that form on the hyphae to initiate ascocarp formation. Also known as perithecial ascomycetes.
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Pyrenomycetes
The largest class in the phylum Ascomycota. The distinguishing feature of these fungi is the ascoma, or perithecium, that gives rise to the common name for the class, perithecial ascomycetes. Most ascomata are brown or black, but some are blue, yellow, or red. Ascomal ontogeny is ascohymenial; coiled branches form on the hyphae to initiate ascoma formation, and they are quickly enveloped by layers of hyphae to form a wall around the coil, which subsequently differentiates into ascogenous hyphae that will form the asci. The internal tissues of the ascoma vary between species. In most species, a neck with a canal forms through which the ascospores will be discharged. The asci are formed in a cluster or layer in the base of the ascoma. Most have a single rigid wall (unitunicate), and the eight ascospores are forcibly discharged through a pore in the apex of the ascus, but in some the ascus wall dissolves. The ascospores are variable in color, size, shape, and number of cells. Most pyrenomycetes also form abundant asexual conidia.
Pyrenomycetes are widespread and occur primarily on living and dead plant materials. They may cause serious disease or act as agents of decomposition, producing a well-developed mycelium that may be superficial or immersed in the host or substrate. See also Ascomycota; Eumycota; Fungi.
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Pyrenomycetes
IN BRIEF: n. - Class of fungi in which the fruiting body is a perithecium.
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McGraw-Hill Science & Technology Dictionary
McGraw-Hill Dictionary of Scientific and Technical Terms. Copyright © 2003, 1994, 1989, 1984, 1978, 1976, 1974 by McGraw-Hill Companies, Inc. All rights reserved.
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McGraw-Hill Science & Technology Encyclopedia
McGraw-Hill Encyclopedia of Science and Technology. Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved.
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