a primary, usually filamentous structure produced by the germination of the spore in mosses and certain related plants, and from which the leafy plant which bears the sexual organs arises as a lateral or terminal shoot.
- pro·to·ne·mal, adjective
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How to use protonema in a sentence
Erect branches may arise from the protonema, and gemmae may be developed on it.
In mosses (fig. 12) a filamentous growth, the protonema, is first formed, and the leafy plants arise upon this.
Usually the protonema is filamentous and ceases to be evident after the plants have developed.
The protonema forms a flat, lobed, thalloid structure attached to the soil by rhizoids, and the plants arise from marginal cells.
The spore on germination forms a short filament which soon broadens out into the thalloid protonema.
British Dictionary definitions for protonema
a branched threadlike structure that grows from a moss spore and eventually develops into the moss plant
- protonemal or protonematal (ˌprəʊtəˈniːmətəl, -ˈnɛmətəl), adjective
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
Scientific definitions for protonema
The green filamentous or flat, thallus-like structure that grows from the germinated spores of liverworts and mosses and eventually gives rise to a mature gametophyte.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.