Studies on the sporogenous lineage in the moss Timmiella barbuloides. IX. Development of the tapetum

The ultrastructure of tapetal cells in Timmiella barbuloides was investigated in relation to events of sporogenesis. After their establishment both internally and externally to the sporogonial initials, tapetal cells enlarge and assume a permanently polarized organization after completion of meiosis...

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Bibliographic Details
Published in:Annals of botany 1994-04, Vol.73 (4), p.369-375
Main Authors: Gambardella, R, Alfano, F, Gargiulo, M, Squillacioti, C
Format: Article
Language:English
Subjects:
B lymphocytes
Biological and medical sciences
Bryophytes
Cell lines
Cell membranes
Cytoplasm
development
Developmental biology
endomembrane dynamics
endoplasmic reticulum
Fundamental and applied biological sciences. Psychology
Materials
mosses and liverworts
nutritive cells
Plant cells
plant development
Plant physiology and development
plasma membrane
Plastids
Pollen
Sexual reproduction
Spores
tapetum
Timmiella
ultrastructure
Vegetative and sexual reproduction, floral biology, fructification
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Summary:The ultrastructure of tapetal cells in Timmiella barbuloides was investigated in relation to events of sporogenesis. After their establishment both internally and externally to the sporogonial initials, tapetal cells enlarge and assume a permanently polarized organization after completion of meiosis. A large vacuole is formed in the cell region distal to the spore sac, the nucleus becomes centrally located, and amyloplasts lie in the cytoplasm adjacent to the spore sac. An extensive endomembrane system develops in tapetal cells during the stage of exine deposition in spore tetrads. Sheets of rough endoplasmic reticulum develop first around the nucleus then also in close proximity to the plasma membrane abutting the spore sac. Concomitantly, intervening dictyosomes produce a variety of vesicles. Unusual structures with vesicle-like profiles also occur in the inner tapetum cell walls abutting the spore sac. At the same time most of the starch is lost from the plastids in which grana-fretwork systems develop. A massive secretion of extremely electron-opaque material is associated with perine deposition onto the free spore surfaces. Degeneration of the tapetal cells during the terminal stages of spore maturation is marked by distortion of the organelles, increase in vacuolation and the appearance of electron-opaque material between the sheets of endoplasmic reticulum.
ISSN:0305-7364
1095-8290
DOI:10.1006/anbo.1994.1046