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  • 1990-1994  (2)
  • 1985-1989  (2)
  • Mitosis  (2)
  • Nicotiana tabacum  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Sexual plant reproduction 4 (1991), S. 104-109 
    ISSN: 1432-2145
    Keywords: High humidity and temperature stress ; Nicotiana tabacum ; Tobacco ; Pollen viability ; Vigour ; Semi-vivo technique
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Responses of pollen grains of Nicotiana tabacum to high humidity (95% RH, 4 h) and temperature (38°/45° C, 4 h) stresses were investigated. Pollen grains were subjected to only RH or only temperature, or to both of these stresses. Their viability was assessed on the basis of the fluorochromatic reaction (FCR) test, and vigour was assessed on the basis of the time taken for in vitro germination as well as on the emergence of pollen tubes through the cut end of semi-vivo implanted styles. None of the stress conditions affected pollen viability and high RH or high temperature stress did not individually affect pollen vigour. However, pollen vigour was markedly affected when both the stresses were given together. Pollen grains subjected to high RH at 38° C took a longer time to germinate in vitro and the pollen tubes emerged later from the cut end of the semi-vivo styles; division of the generative cell was also delayed. Pollen grains subjected to high RH at 45° C failed to germinate in vitro, but did germinate on the stigma. Many pollen tubes subjected to this treatment showed abnormalities, and the growth of pollen tubes in the pistil was much slower than that observed in other treatments. Pollen samples subjected to all of the stress conditions were able to induce fruit and seed set. The implications of these results on the relationship between the FCR test and viability, and between viability and vigour, especially in stressed pollen, are discussed.
    Type of Medium: Electronic Resource
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  • 2
    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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  • 3
    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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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Protoplasma 172 (1993), S. 77-83 
    ISSN: 1615-6102
    Keywords: Ornithogalum virens ; Generative cell ; Mitosis ; Pollen ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Ornithogalum virens is a bicellular pollen species. In mature pollen, the generative nucleus is at advanced prophase. Mitosis of the generative cell is resumed just after pollen rehydration and prometaphase occurs within 10 min of germination. Prometaphase is manifested by nuclear envelope breakdown and the appearance of spindle microtubules in the nucleoplasm region. At this stage the number of cytoplasmic microtubules located in the generative cell periphery appears to decrease. Endoplasmic reticulum-like cisternae originating from the nuclear envelope tend to be spaced around the chromosomes, outside the area of the forming mitotic spindle. Some also begin to penetrate the spindle area. The results are discussed in terms of the generative cell cycle in bicellular pollen.
    Type of Medium: Electronic Resource
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