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  • 2000-2004  (1)
  • 1985-1989  (3)
  • Cytokinesis  (2)
  • Nicotiana tabacum  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Sexual plant reproduction 1 (1988), S. 228-233 
    ISSN: 1432-2145
    Keywords: Microspore mother cell ; Cytokinesis ; Impatiens sultani ; Cell plate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Cytokinesis in Impatiens sultani microspore mother cells is simultaneous. It starts with the formation of small ingrowths of the surrounding callosic wall. Next, an incomplete cell plate is formed by fusion of small dictyosome vesicles. The cell plate consists of a network of anastomosing tubules and sacs. Aggregates of fusing vesicles are associated with bundles of microtubules, which are oriented perpendicular to the plane of the future cell walls. In the sacculate parts of the cell plate, some callose is deposited, while the associated microtubules disappear. The cell walls ultimately develop by enlargement of the previously formed wall ingrowths, which successively incorporate the elements of the cell plate. The enlargement and thickening of the walls is not accompanied by a further fusion and incorporation of dictyosome vesicles.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2145
    Keywords: Key words Cell fusion ; Gamete interaction ; In vitro polygamy ; Nicotiana tabacum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  In vitro polygamy was studied mainly by using isolated sperm and central cells of tobacco in order to elucidate the mechanism that might be involved in preventing in vivo polygamy. In 17.5% 4000 M.W. polyethylene glycol, only when two sperm cells were made close enough to each other and adhered to a female cell simultaneously was polygamy possible. If one sperm cell fused with the egg or central cell, within 30 min another sperm cell could not fuse with the same egg or central cell. Similar phenomena were found in selected single somatic cell fusion. When more than two protoplasts adhered to each other simultaneously, fusion was always successful; after two protoplasts fused, within 30 min the fusion products could not fuse with another protoplast under the same conditions. This comparative study revealed this characteristic to be shared by both sexual and somatic cell fusion. However, after cytoplasm reorganization was complete in the fusion product, it was possible for the fusion product to fuse with the third protoplast. This indicates that the obstruction to additional fusion was present only during a certain period after the preceding fusion under certain condition. The possible reason for the effect is discussed.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Sexual plant reproduction 2 (1989), S. 137-141 
    ISSN: 1432-2145
    Keywords: Humidity ; Temperature stress ; Nicotiana tabacum ; Pollen germination ; Pollen membrane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The prolonged exposure of pollen Nicotiana tabacum to high humidity at both room temperature and 38° C did not affect membrane integrity as revealed by the fluorochromatic reaction (FCR) test, but did affect pollen vigour. At room temperature germination was not affected, although tube growth was reduced; at 38° C, there was both a reduction in tube growth and delayed germination. When the pollen was subjected to 1 h hydration followed by 1 h desiccation (up to a maximum of four cycles) at room temperature, a reduction in the FCR, germination and tube length after each desiccation treatment was observed. Subsequent hydration fully restored the FCR, but only partially restored germination and tube growth. At 38° C, however, FCR, germination, and tube growth were drastically reduced. The implications of these results on the relationship between FCR and germinability, the responses of pollen exposed to humidity and temperature stress in the field, and on pollen storage are discussed.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Protoplasma 150 (1989), S. 54-71 
    ISSN: 1615-6102
    Keywords: Generative cell ; Microtubules ; Mitosis ; Cytokinesis ; Pollen ; Sperm ; Tradescantia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Cytoskeletal organization and chromosome behavior were studied inTradescantia generative cells prior to and during sperm formation using in vitro grown pollen tubes and fluorescence staining methods. Before pollen germination, the crescent-shaped generative cell contains a reticulate microtubule (Mt) system. The cell elongates dramatically after germination, and its Mts assume a helical to longitudinal arrangement. Chromosome condensation is evident approximately 3hr after germination. Kinetochores appear as dark interruptions in the Mt array, and thus seem to attach directly to interphase fibers. No metaphase plate typical of other cells is observed with either DAPI or anti-tubulin staining. Instead, the chromosomes adopt a twisted or braided arrangement, with kinetochores distributed along the length of the cell and kinetochore fibers linked to each other and to surrounding fibers. Anaphase is characterized by a staggered, overlapping separation of chromosomes and by elongation of Mt branches connecting opposing kinetochore fibers. Cytokinesis appears to utilize a furrowing process; a phragmoplast or cell plate was never seen. As a result of these events, the sperm directly inherit their cytoskeleton from generative cell Mts involved in division. No actin fibers are observed at any stage using rhodamine-phalloidin staining. The results are discussed in terms of other reports on sperm formation, possible mitotic and cytokinetic mechanisms, and past distinctions between Mt arrays in higher plant somatic cells.
    Type of Medium: Electronic Resource
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