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  • 1990-1994  (4)
  • 1985-1989  (4)
  • Generative cell  (6)
  • Megagametophyte  (2)
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Material
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Year
Keywords
  • 1
    Electronic Resource
    Electronic Resource
    Ultrastructural features of Aloe ciliaris pollen (1988)
    Springer
    Sexual plant reproduction 1 (1988), S. 88-96 
    Details
    ISSN: 1432-2145
    Keywords: Pollen activation ; Generative cell ; Vegetative cell ; Cytoskeleton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Both the internal anatomy and the external morphology of the mature pollen grain of Aloe ciliaris have been studied, together with the cytological changes occurring during pollen activation. In mature pollen, the generative cell (GC) and the vegetative nucleus (VN) are closely associated with each other, and both can be found in the central part of the grain. In the generative cytoplasm, some organelles and microtubular bundles are present. In the vegetative cell, dictyosomes, stacks of rough endoplasmic reticulum, mitochondria, plastids, vacuoles, ribosomes, and masses of fibrillar material have been described. During pollen activation, important changes occur in both the generative and vegetative cells (VC). In the GC, the microtubular bundles become clearly visible, and the GC and VC gradually move towards the germ pore. The RER cisterns become free from the stacks, and organelles, such as dictyosomes, become very active. The fibrillar masses gradually decrease in number, and the individual fibrils become more evident and clearer in resolution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00189267
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    The microtubule cytoskeleton and the rounding of isolated generative cells ofNicotiana tabacum (1992)
    Springer
    Sexual plant reproduction 5 (1992), S. 64-71 
    Details
    ISSN: 1432-2145
    Keywords: Generative cell ; Isolation ; Microtubules ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Upon squashing of the pollen grain, the isolated generative cell ofNicotiana tabacum looses its spindle shape to become spherical; this phenomenon is independent of the sucrose concentration used. The time necessary for this change can vary from 1 min (0% sucrose) to 20 min (30% sucrose). The microtubular cytoskeleton was studied by means of immunofluorescence and electron microscopy. Just after isolation, 5 to 15 clearly visible bundles in microtubules organized in a basket-like structure are present. After 15 min in medium with 15% sucrose, the microtubular cytoskeleton disappears, and a diffusely spread tubulin can be observed. Neither the addition of 10–20 μM taxol to the medium, nor the omission of Ca2+ to the medium has any effect on the changes in cell shape and loss of microtubular bundles after isolation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00714559
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Pre-fertilization degeneration of both synergids in Brassica campestris ovules (1988)
    Springer
    Sexual plant reproduction 1 (1988), S. 208-216 
    Details
    ISSN: 1432-2145
    Keywords: Megagametophyte ; Synergids ; Brassica campestris ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In Brassica campestris, both synergids of the ovule degenerate before the arrival of the pollen tube. Synergid degeneration does not depend on pollination. At the non-degenerated stage, the synergids are completely filled with a complexly organized cytoplasm containing numerous mitochondria with many cristae, a large number of dictyosomes with many associated vesicles, and a very extensive rough endoplasmic reticulum. The degenerative changes that occur in the cytoplasm of the synergids are characterized by a loss of visibility of the membranes of the endoplasmic reticulum and the simultaneous formation of dense deposits on the surrounding membranes of the mitochondria. Locally, the plasma membranes of the synergids disappear, and some ground plasma of the synergids penetrates into the space between the plasma membranes of the egg cell and the central cell.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00189154
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Video microscopic observations of living, isolated embryo sacs of Nicotiana and their component cells (1992)
    Springer
    Sexual plant reproduction 5 (1992), S. 156-162 
    Details
    ISSN: 1432-2145
    Keywords: Female germ unit ; Nicotiana ; Megagametophyte ; Organelle movement ; Video microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Living embryo sacs and megagametophytic cells of Nicotiana alata and Nicotiana tabacum were obtained using enzymatic maceration and microdissection. The yields of isolated embryo sacs, egg apparatus and central cells were up to 35%, 40% and 35%, respectively. Vectorial movement of organelles and undulations of tubular structures, presumably endoplasmic reticulum, were observed in eggs, synergids and central cells using video-enhanced microscopy. Despite evident viability using the fluorochromatic reaction, the egg displays much less organelle movement and therefore appears to be quiescent. The large vacuole of the central cell is traversed by mobile strands of cytoplasm through which organelles migrate. A polygonal network is located at the periphery of the central cell, which may contribute to anchorage of the cell with the embryo-sac wall. The observation of organelle movement provides direct evidence of the condition of the cell and may be a useful approach for assessing cell vigor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00194876
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Microtubule organization in the sperm ofTradescantia virginiana (1988)
    Springer
    Protoplasma 146 (1988), S. 28-34 
    Details
    ISSN: 1615-6102
    Keywords: Generative cell ; Microtubule ; Sperm ; Pollen ; Tradescantia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Microtubules were visualized in the sperm ofTradescantia virginiana pollen tubes grownin vitro and processed for antitubulin immunocytochemistry. The sperm contain thick microtubule bundles from which emerge numerous branches of various dimensions disposed longitudinally and helically along the cell axis. Sperm are usually spindle or cigar-shaped, but cells of various sizes and shapes can be found. All contain microtubule arrays. No F-actin was detected in sperm using rhodamine-phalloidin staining. Sperm microtubules are discussed in terms of their potential roles in cell shaping and motility and their origin during generative cell division.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01354292
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Cytoskeletal changes during generative cell division and sperm formation inTradescantia virginiana (1989)
    Springer
    Protoplasma 150 (1989), S. 54-71 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF01352921
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  • 7
    Electronic Resource
    Electronic Resource
    The organization of the cytoskeleton in the generative cell and sperms ofHyacinthus orientalis (1992)
    Springer
    Protoplasma 168 (1992), S. 41-50 
    Details
    ISSN: 1615-6102
    Keywords: Pollen tube ; Microtubules ; Cellular division ; Generative cell ; Sperm cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The microtubular cytoskeleton of the generative cell (GC) ofHyacinthus orientalis has been studied until the formation of the sperm cells (SCs). Immunofluorescence procedures in combination with confocal laser scanning microscopy (CLSM) has enabled the visualization of the organization of the microtubular cytoskeleton. Chemical fixation and freeze-fixation electron microscopy have been used to investigate the cytoskeleton and the ultrastructural organization of the GC and SCs. During pollen activation the GC is spindle-shaped. Microtubules (MTs) are organized as bundles and distributed in proximity of the GC plasmamembrane, forming a basket-like structure. Following migration through the pollen tube, the basket-like structure becomes more intertwined. During the nuclear division the MTs are involved in the segregation of the chromosomes and kinetochores are clearly discernible. Association with organelles is also observed. The chromosomes of the GC remain condensed until they separate in two sperm nuclei. The pre-prophase band was never observed. At the end of the GC division the microtubular network reorganizes in the two SCs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01332649
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    Paper (German National Licenses)
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  • 8
    Electronic Resource
    Electronic Resource
    Early events in division of the generative cell ofOrnithogalum virens (1993)
    Springer
    Protoplasma 172 (1993), S. 77-83 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF01379365
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