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  • 1
    Electronic Resource
    Electronic Resource
    Ultrastructure and histochemistry of Citrus limon (L.) stigma (1982)
    Springer
    Planta 156 (1982), S. 1-9 
    Details
    ISSN: 1432-2048
    Keywords: Citrus ; Development (stigma) ; Exudate (stigmatic) ; Stigma (histochemistry, ultrastructure)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Citrus limon has a “wet” stigma which can be divided in two zones: a glandular superficial one formed by papillae, and a non-glandular one formed by parenchymatic cells. The stigmatic exudate is produced by the papillae after the latter have reached their ultimate size. The papillae of the mature pistil are of varying size and composition. Both the unicellular and multicellular ones are present. The cells at the base of the papillae are rich in cytoplasm, whereas the tip cells are vacuolated. Histochemical analysis has shown that the exudate of Citrus is composed of lipids, polysaccharides, and proteins. Our results indicate that the lipidic component is produced and secreted first, followed by production and secretion of the polysaccharidic component. The lipidic component of the exudate is produced in the basal papillae cells and accumulates as droplets in dilated parts of the smooth endoplasmic reticulum (SER). Subsequently the lipid droplets are transported to the plasma membrane, and transferred by the latter into the cell walls. Then the exudate component is accumulated in the intercellular spaces and in the middle lamellar regions of the walls. Subsequently, the polysaccharidic component of the exudate is produced and secreted by the tip cells of the papillae.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00393436
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  • 2
    Electronic Resource
    Electronic Resource
    Ultrastructural investigations on Lycopersicum peruvianum pollen activation and pollen tube organization after self-and cross-pollination (1980)
    Springer
    Planta 150 (1980), S. 211-217 
    Details
    ISSN: 1432-2048
    Keywords: Lycopersicum ; Pollen activation ; Pollen tube ; Self-incompatibility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract No differences have been observed “in vivo” between Lycopersicum peruvianum compatible and incompatible pollen during activation and pollen tube emission and organization, that is until 4 h and 30 min after pollination. During pollen activation the main events are the setting free of rough endoplasmic reticulum (RER) cisterns which were “stacked” in the mature pollen, the increase in the number of polysomes, and a great activity of the dictyosomes. Immediately after germination of the vegetative nucleus and the generative cell move into the tube, the generative cell diviting to form the male gametes; the tube then becomes organized in four zones. This series of changes is similar to what has already been observed “in vitro” except that in vitro the generative cell remains undivided and the whole process from seeding to tube organization takes 3 h instead of 4 h and 30 min after pollination, as it does in vivo. Our findings are compatible with the main models of the tube inhibition mechanism proposed till now.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00390828
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  • 3
    Electronic Resource
    Electronic Resource
    Rethinking cytoskeleton in plant reproduction: toward a biotechnological future? (1999)
    Springer
    Sexual plant reproduction 12 (1999), S. 67-70 
    Details
    ISSN: 1432-2145
    Keywords: Key words Cytoskeleton ; Cytoskeleton proteins ; Cytoskeleton function ; Pollen tube ; Embryo sac
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Sexual reproduction in plants is intimately connected to the activity of the cytoskeletal apparatus in reproductive cells. Because of the ease with which the pollen tube can be studied, it has become a model for studying many aspects of cell physiology related to the cytoskeleton, such as movement of organelles and vesicles and cell division. However, information about cytoskeletal proteins is still insufficient for determining cytoskeletal functions during reproduction, especially in terms of cell-cell interactions. One reason may be that cytological and biochemical research on the cytoskeleton of pollen and the embryo sac has not been complemented by sufficient research activity at genetic and molecular levels, and few laboratories are currently involved in this work. This might be because of problems in identifying appropriate applied applications of the work that might attract more investigation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004970050173
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  • 4
    Electronic Resource
    Electronic Resource
    Localization of ubiquitin in anthers and pistils of Nicotiana (1995)
    Springer
    Sexual plant reproduction 8 (1995), S. 123-128 
    Details
    ISSN: 1432-2145
    Keywords: Anther ; Pistil ; Plant reproduction ; Pollen Transmitting tissue ; Ubiquitin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Ubiquitin-conjugated compounds were localized in anthers and pistils of Nicotiana alata by immuno-cytochemistry. In young anthers, antibodies to ubiquitin bound to callose cell walls surrounding pollen mother cells and to organelles in the endothecium. At the freespore stage, antibodies bound to circular-cell cluster cells subtending the stomium and to organelles and cell walls of endothecial cells. Near anther dehiscence, locular material was labeled. In pistils, cell walls of stylar transmitting tissue were labeled in a beaded pattern. Antibodies bound to a thin layer surrounding ovules, to the lining of embryo sacs, to cytoplasm of eggs and synergids, and to starch grains in central cells. Sites of localization were tissue- and time-specific, suggesting a regulatory role for ubiquitin in development of reproductive structures in flowering plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00242254
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  • 5
    Electronic Resource
    Electronic Resource
    Cytoplasmic motors and pollen tube growth (1996)
    Springer
    Sexual plant reproduction 9 (1996), S. 59-64 
    Details
    ISSN: 1432-2145
    Keywords: Motor proteins ; Pollen tube ; Tip growth ; Organelle movement
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The growth of pollen tubes is characterized by an intense cytoplasmic streaming, during which the movements of smaller organelles (like secretory vesicles) and larger ones (including the generative cell and vegetative nucleus) are precisely coordinated. A well-characterized cytoskeletal apparatus is likely responsible for these intracellular movements. In recent years both microfilament and microtubule-based motor proteins have been identified and assumed to be the translocators of the several organelle categories. Their precise function during pollen tube growth is not yet clear, but apparently an actomyosin-based system is mainly responsible for pollen tube elongation. On the other hand, microtubules and microtubule-based motors have been thought to play a role in the maintenance of cell polarity. Both cytoskeletal systems (and their respective motor activities) could cooperate to ensure a precise regulation of pollen tube growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02153052
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  • 6
    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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  • 7
    Electronic Resource
    Electronic Resource
    Cytoplasmic motors and pollen tube growth (1996)
    Springer
    Sexual plant reproduction 9 (1996), S. 59-64 
    Details
    ISSN: 1432-2145
    Keywords: Key words Motor proteins ; Pollen tube ; Tip growth ; Organelle movement
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The growth of pollen tubes is characterized by an intense cytoplasmic streaming, during which the movements of smaller organelles (like secretory vesicles) and larger ones (including the generative cell and vegetative nucleus) are precisely coordinated. A well-characterized cytoskeletal apparatus is likely responsible for these intracellular movements. In recent years both microfilament- and microtubule-based motor proteins have been identified and assumed to be the translocators of the several organelle categories. Their precise function during pollen tube growth is not yet clear, but apparently an actomyosin-based system is mainly responsible for pollen tube elongation. On the other hand, microtubules and microtubule-based motors have been thought to play a role in the maintenance of cell polarity. Both cytoskeletal systems (and their respective motor activities) could cooperate to ensure a precise regulation of pollen tube growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004970050011
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  • 8
    Electronic Resource
    Electronic Resource
    Growth inhibition and recovery in freeze-substitutedLilium longiflorum pollen tubes: structural effects of caffeine (1997)
    Springer
    Protoplasma 196 (1997), S. 21-33 
    Details
    ISSN: 1615-6102
    Keywords: Caffeine ; Freeze substitution ; Lilium ; Pollen tubes ; Rapid freeze fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In an attempt to correlate structural effects with the known dissipation of the tip-focused Ca2+ gradient caused by caffeine, we have examined the ultrastructure of caffeine-treated lily pollen tubes prepared by rapid freeze fixation and freeze substitution. We show that treatment with caffeine results in a rapid rearrangement of secretory vesicles at the pollen tube tip; the normal cone-shaped array of vesicles is rapidly dispersed. In addition, microfilament bundles appear in the tip region, where they had previously been excluded. Delocalized vesicle fusion continues in the presence of caffeine but tube extension ceases. Removal of caffeine from the growth medium initially causes tip swelling, delocalized vesicle fusion and presence of microfilaments well into the tip before normal structure and growth resume, concurrent with the previously reported return to a normal Ca2+ gradient.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01281055
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  • 9
    Electronic Resource
    Electronic Resource
    Ultrastructural immunolocalization of periodic pectin depositions in the cell wall ofNicotiana tabacum pollen tubes (1995)
    Springer
    Protoplasma 187 (1995), S. 168-171 
    Details
    ISSN: 1615-6102
    Keywords: Cell wall ; Immunocytochemical localization ; JIM5 antibody ; Pectins ; Pollen tube
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The monoclonal antibody (MAb) JIM5, marking acidic pectins, was used to localize ultrastructurally pectin molecules in the pollen tube wall ofNicotiana tabacum. Longitudinal sections of LR-White embedded pollen tubes were exposed to antibody treatment; accumulations of pectins were identified by counting the density of the gold particles representing the pectin epitopes along the pollen tube wall. Significant accumulations of gold grains were marked and the distances between them were measured. In many pollen tubes a more or less regular distribution of the accumulations was observed along the tube indicating a periodical deposition of pectin. The distances between the accumulations were 4–6 μm. Most of the label was found in the inner part of the outer layer of the bilayered cell wall. These findings correspond to and confirm the earlier observation by our group reporting ring-shaped periodical deposits in pollen tubes after immunofluorescence labelling with the MAb JIM5 under the confocal laser scanning microscope.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01280245
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  • 10
    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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