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  • Cytoskeleton  (4)
  • Microtubules  (4)
  • Gamete interaction  (2)
  • Megagametophyte  (2)
  • 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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  • 2
    Electronic Resource
    Electronic Resource
    In vitro double fertilization in Nicotiana tabacum (L.): fusion behavior and gamete interaction traced by video-enhanced microscopy (2000)
    Springer
    Sexual plant reproduction 12 (2000), S. 267-275 
    Details
    ISSN: 1432-2145
    Keywords: Key words Nicotiana tabacum ; In vitro fertilization ; Gamete interaction ; Cytology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  In vitro double fertilization in tobacco was carried out with attention to fusion behavior and gamete interaction. Structural and cytological events indicating possible reaction to the fusion of sperm-egg and especially sperm-central cell were recorded by video-enhanced microscopy. Generative cells were fused with the egg cell or central cell as a control system to better understand gamete interaction. As early as adherence of the male cell, the female cell showed response by means of cytoplasm strand formation. After gamete fusion, cytoplasm activation in the egg cell was observed as long distance movement of organelles. In fertilized central cells, however, fusion did not result in notable cytological change within 30 min. Male nuclear movement recorded in the female cell illustrated two different patterns of movement which showed similarity to organelle movement. The dynamics of male and female nuclear fusion after in vitro fertilization was also recorded in the central cell. It revealed that the fusion process requires only a few seconds and is similar to that of gamete fusion in vitro. This may offer a new clue for understanding how female and male nuclei attract, adhere and finally fuse each other.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004970050194
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  • 3
    Electronic Resource
    Electronic Resource
    In vitro double fertilization in Nicotiana tabacum (L.): polygamy compared with selected single pair somatic protoplast and chloroplast fusions (2000)
    Springer
    Sexual plant reproduction 13 (2000), S. 113-117 
    Details
    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
    URL: http://dx.doi.org/10.1007/s004970000044
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  • 4
    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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  • 5
    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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  • 6
    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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  • 7
    Electronic Resource
    Electronic Resource
    Striped projections of the outer membrane of the generative cell in Convallaria majalis pollen (1995)
    Springer
    Sexual plant reproduction 8 (1995), S. 223-227 
    Details
    ISSN: 1432-2145
    Keywords: Pollen ; Generative cell ; Cytoskeleton ; Motility ; Myosin immunogold labelling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In pollen grains of Convallaria majalis the outer membrane of the generative cell (GC) is the inner membrane of the vegetative cell (VC). Striped projections (SP) at the cytoplasmic face of the outer membrane of the GC were revealed by chemical fixation and also by a rapid freeze-fixation and freeze-substitution. The projections, located in groups on the protruding lobes of the GC, were arranged parallel to each other and were equally spaced (40 nm apart). The length of the SP, estimated from grazing sections of GC, was 400 nm. Each projection was composed of T-shaped elements, about 35 nm high, spaced at an average distance of 25 nm. SP were observed in mature, hydrated, activated and germinated pollen grains and seemed to be associated with microtubules and microfilaments of the VC. No evidence exists yet of SP on the sperm cell membrane. Immunogold labelling with anti-myosin antibodies showed many gold particles attached preferentially to the surface of the protruding lobes of the GC in the area of the projections. These results may suggest that the SP of Convallaria GC contain myosin-like protein and play an important role in the motility of the GC during pollen tube growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00228941
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  • 8
    Electronic Resource
    Electronic Resource
    The organization of microtubules during generative-cell division inConvallaria majalis (1999)
    Springer
    Protoplasma 207 (1999), S. 147-153 
    Details
    ISSN: 1615-6102
    Keywords: Cell division ; Confocal microscopy ; Convallaria majalis ; Generative cell ; Liliaceae ; Microtubules
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The organization of the microtubule cytoskeleton in the generative cell ofConvallaria majalis has been studied during migration of the cell through the pollen tube and its division into the two sperm cells. Analysis by conventional or confocal laser scanning microscopy after tubulin staining was used to investigate changes of the microtubule cytoskeleton during generative-cell migration and division in the pollen tube. Staining of DNA with 4′,6-diamidino-2-phenylindole was used to correlate the rearrangement of microtubules with nuclear division during sperm cell formation. Before pollen germination the generative cell is spindle-shaped, with microtubules organized in bundles and distributed in the cell cortex to form a basketlike structure beneath the generative-cell plasma membrane. During generative-cell migration through the pollen tube, the organization of the microtubule bundles changes following nuclear division. A typical metaphase plate is not usually formed. The generative-cell division is characterized by the extension of microtubules concomitant with a significant cell elongation. After karyokinesis, microtubule bundles reorganize to form a phragmoplast between the two sperm nuclei. The microtubule organization during generative-cell division inConvallaria majalis shows some similarities but also differences to that in other members of the Liliaceae.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01282994
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  • 9
    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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  • 10
    Electronic Resource
    Electronic Resource
    Ultrastructure of the cytoskeleton in freeze-substituted pollen tubes ofNicotiana alata (1987)
    Springer
    Protoplasma 140 (1987), S. 141-150 
    Details
    ISSN: 1615-6102
    Keywords: Cytoskeleton ; Freeze substitution ; Nicotiana ; Pollen tubes ; Rapid freeze fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The ultrastructure of the cytoskeleton inNicotiana alata pollen tubes grownin vitro has been examined after rapid freeze fixation and freeze substitution (RF-FS). Whereas cytoplasmic microtubules (MTs) and especially microfilaments (MFs) are infrequently observed after conventional chemical fixation, they occur in all samples prepared by RF-FS. Cortical MTs are oriented parallel to the long axis of the pollen tube and usually appear evenly spaced around the circumference of the cell. They are always observed with other components in a structural complex that includes the following: 1. a system of MFs, in which individual elements are aligned along the sides of the MTs and crossbridged to them; 2. a system of cooriented tubular endoplasmic reticulum (ER) lying beneath the MTs, and 3. the plasma membrane (PM) to which the MTs appear to be extensively linked. The cortical cytoskeleton is thus structurally complex, and contains elements such as MFs and ER that must be considered together with the MTs in any attempt to elucidate cytoskeletal function. MTs are also observed within the vegetative cytoplasm either singly or in small groups. Observations reveal that some of these may be closely associated with the envelope of the vegetative nucleus. MTs of the generative cell, in contrast to those of the vegetative cytoplasm, occur tightly clustered in bundles and show extensive cross-bridging. These bundles, especially in the distal tail of the generative cell, are markedly undulated. MFs are observed commonly in the cytoplasm of the vegetative cell. They occur in bundles oriented predominantly parallel to the pollen tube axis. Although proof is not provided, we suggest that they are composed of actin and are responsible for generating the vigorous cytoplasmic streaming characteristic of living pollen tubes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01273723
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