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  • 1
    Electronic Resource
    Electronic Resource
    Isolation of male and female gametes in higher plants (1991)
    Springer
    Sexual plant reproduction 4 (1991), S. 145-154 
    Details
    ISSN: 1432-2145
    Keywords: Angiosperm gametes ; Egg cell ; Embryosac ; Gamete isolation ; Gametophytic cells ; Sperm cells ; Generative cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The availability of generative cells, sperm cells, embryo sacs and egg cells from angiosperm plants in isolated conditions has opened up many prospects: study of the mechanism of recognition and fusion between gametes of opposite sex and detailed observation of the process of fertilization, biochemical and genetic analysis of gamete-specific components and genetic engineering in combination with in vitro fertilization. This review provides a list of about ninety publications, in which the isolation of male or female angiosperm gametes and the closely related generative cells and embryo sacs is reported. The species used are summarized in two tables. A description is given of the diverse isolation techniques, which consist of enzymatic digestion, bursting of pollen by osmotic shock, squashing, grinding and micro-dissection. Viability of isolated cells and yield, two important aspects of biotechnological manipulation, are emphasized. A critical evaluation of the most significant results obtained so far with isolated material is presented together with notes on prospects for the future.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00189998
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Origin of sperm cell association in the “male germ unit” ofBrassica pollen (1989)
    Springer
    Protoplasma 149 (1989), S. 1-4 
    Details
    ISSN: 1615-6102
    Keywords: Brassica napus ; Cell division ; Male germ unit ; Pollen ; Sperm cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The association of the two sperm cells inBrassica napus pollen following the generative cell division was investigated. The generative cell during division is located in the center of the pollen grain, within the vegetative cell. The space present between the two cells is slightly irregular as seen following standard glutaraldehyde fixation. After completion of mitosis vesicles appear in the equatorial plane, coalescing centripetally to form a cell plate which fuses with the membrane of the generative cell, dividing it in two sperm cells. They are isolated from the vegetative cell by the space between the two cell membranes and are separated from each other by a similar space resulting from the cell plate formed during cytokinesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01623975
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    Paper (German National Licenses)
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  • 3
    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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    Paper (German National Licenses)
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  • 4
    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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  • 5
    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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