Teratisms in living and fossil megaspores of the Lycopsida: tetrad arrangement and exine ontogeny

Abnormal megaspore tetrad configurations fromSelaginella laevigataand ofLagenicula crassiaculeata(Lower Carboniferous) have been studied by SEM. These abnormalities reflect the variation expected in the presumed evolution of the seed-plants from free-sporing heterosporous ancestors. In addition, the...

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Bibliographic Details
Published in:Botanical journal of the Linnean Society 1997-09, Vol.125 (1), p.1-24
Main Author: HEMSLEY, ALAN R
Format: Article
Language:English
Subjects:
colloidal self-assembly
spore wall development
sporopollenin
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Summary:Abnormal megaspore tetrad configurations fromSelaginella laevigataand ofLagenicula crassiaculeata(Lower Carboniferous) have been studied by SEM. These abnormalities reflect the variation expected in the presumed evolution of the seed-plants from free-sporing heterosporous ancestors. In addition, they indicate a possible role for the aborted members of a tetrad in the successful development and maturation of the functional spore(s). Aborted members of tetrads also reveal the later stages of the developmental sequence occurring in spore wall construction and highlight the interplay of sporopollenin production, its colloidal flocculation and polymerization, and distortion caused by protoplast expansion. Possible causes of abortion in both living and extinct lycopsid megaspores are discussed.
ISSN:0024-4074
1095-8339
DOI:10.1006/bojl.1997.9999