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  • 1
    ISSN: 1432-2048
    Keywords: Cytokinesis ; Generative cell ; Mitosis ; Ornithogalum ; Phragmoplast ; Pollen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The organization of the microtubule (Mt) cytoskeleton during mitosis and cytokinesis of the generative cell (GC) in Ornithogalum virens L. (bicellular pollen type, chromosome number, n = 3) from prophase to telophase/sperm formation was investigated by localization of α-tubulin immunofluorescence using a conventional fluorescence microscope and a confocal laser scanning microscope. Chromosomes were visualized with DNA-binding fluorochrome dyes (ethidium bromide and 4′6-diamino-2-phenyl-indole). The GC of O. virens is characterized by G2/M transition within the pollen grain and not in the pollen tube as occurs in the majority of species with bicellular pollen. It was found that prophase in the GC starts before anthesis and prometaphase takes place after 10 min of pollen germination. The prophase Mts are organized into three prominent bundles, located near the generative nucleus. The number of these Mt bundles is the same as the number of GC chromosomes, a relation which has not previously been considered in other species. The most evident feature in the prophase/ prometaphase transition of O. virens GC is a direct rapid rearrangement of Mt bundles into a network which appears to interact with kinetochores and form a typical prometaphase Mt organization. The metaphase chromosomes are arranged into a conventional equatorial plate, and not in tandem as is thought to be characteristic of GC metaphase. The metaphase spindle consists of kinetochore fibres and a few interzonal fibres which form dispersed poles. Anaphase is characterized by a significant elongation of the mitotic spindle concomitant with the extension of the distance between the opposite poles. At anaphase the diffuse poles converge. Cytokinesis is realized by cell plate formation in the equatorial plane of the GC. The phragmoplast Mts between two future sperm nuclei appear after Mts of the mitotic spindle have disappeared.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Sexual plant reproduction 9 (1996), S. 312-317 
    ISSN: 1432-2145
    Keywords: Pollen tube ; Nicotiana tabacum ; Ginkgo biloba ; Dynein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Microtubules in pollen tubes are evident within the vegetative and generative cell cytoplasm. This observation led to the formulation of several hypotheses regarding the role of microtubules in cytoplasmic movement and the migration of the vegetative nucleus/generative cell along the pollen tube. The study of microtubular motor proteins in pollen tubes followed the discovery and characterization of an immunoreactive homolog of mammalian kinesin in tobacco pollen tubes. Recent identification of dynein-related polypeptides in pollen tubes ofNicotiana tabacum and pollen ofGinkgo biloba is a significant step in the definition of the role of microtubule function within pollen and pollen tubes.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Sexual plant reproduction 1 (1988), S. 240-247 
    ISSN: 1432-2145
    Keywords: Cell division ; Pollen ; Generative cell ; Sperm cells ; Hordeum vulgare L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Shortly before and during division, the generative cell of barley (Hordeum vulgare L.) is located near the vegetative nucleus, in the peripheral layer of the highly vacuolated vegetative cell at the aperture pole. This position is also characteristic of the two resulting sperm cells. Conventional mitosis of the generative cell is followed by cytokinesis through cell plate formation. Just after division, the two sperm cells are enclosed together within a common “inner” vegetative cell plasma membrane, and they gradually separate from each other only during pollen maturation. The space between the generative or sperm cell plasma membrane and the vegetative cell plasma membrane is very thin and appears to be devoid of a cell wall. Both the generative cell and the young sperm cells contain a normal set of organelles; plastids devoid of starch are only sporadically observed. Our data indicate that in Hordeum vulgare the generative cell divides after migrating inside the pollen grain. This follows the pattern of development well established for several species with tricellular pollen.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Sexual plant reproduction 9 (1996), S. 312-317 
    ISSN: 1432-2145
    Keywords: Key words Pollen tube ; Nicotiana tabacum ; Ginkgo biloba ; Dynein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Microtubules in pollen tubes are evident within the vegetative and generative cell cytoplasm. This observation led to the formulation of several hypotheses regarding the role of microtubules in cytoplasmic movement and the migration of the vegetative nucleus/generative cell along the pollen tube. The study of microtubular motor proteins in pollen tubes followed the discovery and characterization of an immunoreactive homolog of mammalian kinesin in tobacco pollen tubes. Recent identification of dynein-related polypeptides in pollen tubes of Nicotiana tabacum and pollen of Ginkgo biloba is a significant step in the definition of the role of microtubule function within pollen and pollen tubes.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1615-6102
    Keywords: Nicotiana tabacum ; Pollen ; Pollen tube ; Cell wall ; Immunogold localization ; Pectins ; Arabinogalactan proteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The monoclonal antibodies JIM 5 (against unesterified pectin), JIM 7 (against methyl esterified pectin), MAC 207 (against arabinogalactan proteins, AGPs), and JIM 8 (against a subset of AGPs) were utilized singly or in combinations for immunogold labelling of germinated pollen grains and pollen tubes ofNicotiana tabacum. Pectins were localized in the inline of pollen grain, unesterified pectin being more abundant than the esterified one. AGPs were co-localized with pectin in the inline, but were present preferably close to the plasma membrane. In pollen tubes, AGPs, unesterified and esterified pectins were co-localized in the outer and middle layers of the cell wall. The density of the epitopes was not uniform along the length of the pollen tube, but showed alterations. In the pollen tube tip wall esterified pectin was abundantly present, but not AGPs. In the cytoplasm esterified pectin and AGPs were detected in Golgi derived vesicles, indicating their role in the pathway of the cell wall precursors. In the “cell wall” of generative cell only AGPs, but no pectins were localized. The co-localization of pectins and AGPs in the cell wall of pollen grain and pollen tube might play an important role, not only in maintenance of the cell shape, but also in cell-cell interaction during pollen tube growth and development.
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