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  • 1
    Electronic Resource
    Electronic Resource
    Some events of mitosis and cytokinesis in the generative cell of Ornithogalum virens L. (1996)
    Springer
    Planta 199 (1996), S. 202-208 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF00196560
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  • 2
    Electronic Resource
    Electronic Resource
    Generative cell division and sperm cell formation in barley (1988)
    Springer
    Sexual plant reproduction 1 (1988), S. 240-247 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00189159
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  • 3
    Electronic Resource
    Electronic Resource
    Localization of pectins in the pollen tube wall of Ornithogalum virens L. Does the pattern of pectin distribution depend on the growth rate of the pollen tube? (2000)
    Springer
    Planta 210 (2000), S. 630-635 
    Details
    ISSN: 1432-2048
    Keywords: Key words: Cell wall – Growth rate –Ornithogalum– Pectin – Pollen tube
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Monoclonal antibodies that recognize pectins were used for the localization of esterified (JIM7) and acidic, unesterified (JIM5) forms of pectin in pollen tube walls of Ornithogalum virens L. (x = n = 3). The results indicated that the distribution of the two forms of pectin in the pollen tube wall depended on the medium (liquid or solid) used for pollen germination. In pollen tubes grown in the liquid medium, the localization of JIM7 was limited to the very tip of the pollen tube, whereas the localization of JIM5 indicated a uniform distribution of unesterified pectins in the very tip of the tube and along the subapical parts of the tube wall. In tubes germinated on the medium stabilized with agar (1–2%) the localization of JIM7 and JIM5 indicated the presence of both forms of pectin in the tube tip and along the whole length of the pollen tube wall in a ring-like pattern. Thus, the localization of esterified pectins in the sub-apical part of the pollen tube wall, below the apex of the tube, is described for the first time. Measurements of the growth rates of pollen tubes growing on the two types of medium indicated that oscillations in tube growth rate occur but these do not coincide with the pattern of pectin distribution in the tube wall. Our results complement the previous data obtained for the localization of JIM5 and JIM7 in pollen tube walls of other plant species. (Y.-Q. Li et al. 1994, Sex Plant Reprod 7: 145–150) and provide new insight into an understanding of the construction of the pollen tube wall and the physiology of pollen grain germination.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004250050053
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  • 4
    Electronic Resource
    Electronic Resource
    Ultrastructure of the vegetative cell ofBrassica napus pollen with particular reference to microbodies (1989)
    Springer
    Protoplasma 152 (1989), S. 22-28 
    Details
    ISSN: 1615-6102
    Keywords: Brassica napus ; Vegetative cell ; Microbodies ; Pollen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The ultrastructure of the vegetative cell ofBrassica napus tricellular pollen grains, just before anthesis with standard chemical fixation, is reported. The vegetative cell may be regarded as a highly differentiated and metabolically active fat-storage cell. It contains many mitochondria with a well developed internal membrane system, starchless plastids, microbodies, lipid bodies, dictyosomes and numerous vesicles thought to originate from the dictysomes. Rough endoplasmic reticulum organized in stacks of cisternae is also spatially associated with certain organelles, mainly lipid bodies, microbodies and plastids. There are also randomly distributed polyribosome areas. The microbodies are mainly polymorphic in shape and are often observed in contact with lipid bodies. The above spatial relationship implies that the microbodies may have a glyoxysomal function. In the late period of vegetative cell maturation, the microbodies are probably involved in the process of glyconeogenesis in which the conversion of lipid reserves to sugar takes place.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01354236
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  • 5
    Electronic Resource
    Electronic Resource
    Microspore ofSecale cereale as a transfer cell type (1990)
    Springer
    Protoplasma 158 (1990), S. 26-32 
    Details
    ISSN: 1615-6102
    Keywords: Secale ; Microspore ; Pollen wall ingrowths ; Transfer cells ; Plasmatubules ; Pollen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In the mature microspore ofSecale cereale, a set of wall ingrowths deposited as the first (outer) intine layer between exine and the microspore plasma membrane, are revealed by electron microscopy. The wall ingrowths form a girdle in the vicinity of the apertural region at the external pole of microspore which is in contact with the tapetum, so the microspore can be considered as a transfer cell which is polarized. After microspore division the second (inner) intine layer is deposited by the vegetative cell and forms a labyrinth of branched wall ingrowths. As a result, the periphery of a vegetative cell is also irregular and appears as very thin plasmatubules or evaginations delimited by plasma membrane and penetrating the pollen wall. The possible functions of the microspore as a transfer cell and the wall-membrane system of the vegetative cell are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01323270
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  • 6
    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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  • 7
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    Some events of mitosis and cytokinesis in the generative cell of Ornithogalum virens L. (1996)
    Springer
    Details
    Publication Date: 1996-06-01
    Print ISSN: 0032-0935
    Electronic ISSN: 1432-2048
    Topics: Biology
    Published by Springer
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  • 8
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    Localization of pectins in the pollen tube wall of Ornithogalum virens L. Does the pattern of pectin distribution depend on the growth rate of the pollen tube? (2000)
    Springer
    Details
    Publication Date: 2000-03-17
    Print ISSN: 0032-0935
    Electronic ISSN: 1432-2048
    Topics: Biology
    Published by Springer
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