protosporen.
/ˈprəʊtə(ʊ)spɔː/, U.S. /ˈproʊdəˌspɔr/ 1. Mycology. Originally: an early stage in fungal spore development believed to be analogous to the prothallus in ferns. In later use: spec. a uninucleate segment formed by the cleavage of a multinucleate mass of cytoplasm from which the spore or sporangium develops.
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1865 M. C. Cooke in Amer. Naturalist 2 566 Our number represents only the actual proto-spores which are contained within the cups.
1888 W. W. Meech Quince Culture 88 Each of the protospores contained within the peridia may germinate, and produce not only one, but many vegetative spores.
1900 R. A. Harper in Bot. Gaz. 30 238 [In Fuligo] the uninucleated segments formed by the completion of the cleavage process, and which I have called protospores, become the functional spores directly.
1955 Bull. Torrey Bot. Club 82 233 Following completion of cleavage the protospore nucleus divides, and the protospore develops into a multinucleate sporangium.
1975 Proc. National Acad. Sci. U.S.A. 72 4076/1 The germspores are homokaryotic, possibly because they are formed from protospores containing only one nucleus.
2. Biology. In a slime mould: a uninucleate segment of a multinucleate fruiting body from which the spore develops.
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1908 New Phytologist 7 82 The peripheral protoplasm is thus cut up into numerous uninucleate masses which may be called ‘protospores’.
1934 T. H. Macbride & G. W. Martin Myxomycetes 5 When the sporophores are mature, the surface becomes marked off into polyhedral, uninucleate protospores, each of which becomes elevated upon a slender stalk.
1977 Amer. Jrnl. Bot. 64 114/1 Following cytokinesis, the resulting uninucleate, irregularly-shaped masses of cytoplasm (protospores) rounded up..and secreted the warts.
This entry has been updated (OED Third Edition, September 2007; most recently modified version published online March 2022).
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