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  • Nicotiana tabacum  (5)
  • Brassica napus  (3)
  • Sperm cells  (3)
  • Freeze substitution  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Biology of the Cell 79 (1993), S. 125-132 
    ISSN: 0248-4900
    Keywords: Nicotiana tabacum ; acetylated α-tubulin ; confocal laser scanning microscope ; microtubules ; pollen tube growth ; tyrosinated α-tubulin
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 2
    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
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Sexual plant reproduction 2 (1989), S. 137-141 
    ISSN: 1432-2145
    Keywords: Humidity ; Temperature stress ; Nicotiana tabacum ; Pollen germination ; Pollen membrane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The prolonged exposure of pollen Nicotiana tabacum to high humidity at both room temperature and 38° C did not affect membrane integrity as revealed by the fluorochromatic reaction (FCR) test, but did affect pollen vigour. At room temperature germination was not affected, although tube growth was reduced; at 38° C, there was both a reduction in tube growth and delayed germination. When the pollen was subjected to 1 h hydration followed by 1 h desiccation (up to a maximum of four cycles) at room temperature, a reduction in the FCR, germination and tube length after each desiccation treatment was observed. Subsequent hydration fully restored the FCR, but only partially restored germination and tube growth. At 38° C, however, FCR, germination, and tube growth were drastically reduced. The implications of these results on the relationship between FCR and germinability, the responses of pollen exposed to humidity and temperature stress in the field, and on pollen storage are discussed.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Sexual plant reproduction 4 (1991), S. 104-109 
    ISSN: 1432-2145
    Keywords: High humidity and temperature stress ; Nicotiana tabacum ; Tobacco ; Pollen viability ; Vigour ; Semi-vivo technique
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Responses of pollen grains of Nicotiana tabacum to high humidity (95% RH, 4 h) and temperature (38°/45° C, 4 h) stresses were investigated. Pollen grains were subjected to only RH or only temperature, or to both of these stresses. Their viability was assessed on the basis of the fluorochromatic reaction (FCR) test, and vigour was assessed on the basis of the time taken for in vitro germination as well as on the emergence of pollen tubes through the cut end of semi-vivo implanted styles. None of the stress conditions affected pollen viability and high RH or high temperature stress did not individually affect pollen vigour. However, pollen vigour was markedly affected when both the stresses were given together. Pollen grains subjected to high RH at 38° C took a longer time to germinate in vitro and the pollen tubes emerged later from the cut end of the semi-vivo styles; division of the generative cell was also delayed. Pollen grains subjected to high RH at 45° C failed to germinate in vitro, but did germinate on the stigma. Many pollen tubes subjected to this treatment showed abnormalities, and the growth of pollen tubes in the pistil was much slower than that observed in other treatments. Pollen samples subjected to all of the stress conditions were able to induce fruit and seed set. The implications of these results on the relationship between the FCR test and viability, and between viability and vigour, especially in stressed pollen, are discussed.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Sexual plant reproduction 4 (1991), S. 176-181 
    ISSN: 1432-2145
    Keywords: Pollen ; Brassica napus ; Mitoses ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Brassica napus pollen development during the formation of the generative cell and sperm cells is analysed with light and electron microscopy. The generative cell is formed as a small lenticular cell attached to the intine, as a result of the unequal first mitosis. After detaching itself from the intine, the generative cell becomes spherical, and its wall morphology changes. Simultaneously, the vegetative nucleus enlarges, becomes euchromatic and forms a large nucleolus. In addition, the cytoplasm of the vegetative cell develops a complex ultrastructure that is characterized by an extensive RER organized in stacks, numerous dictyosomes and Golgi vesicles and a large quantity of lipid bodies. Microbodies, which are present at the mature stage, are not yet formed. The generative cell undergoes an equal division which results in two spindle-shaped sperm cells. This cell division occurs through the concerted action of cell constriction and cell plate formation. The two sperm cells remain enveloped within one continuous vegetative plasma membrane. One sperm cell becomes anchored onto the vegetative nucleus by a long extension enclosed within a deep invagination of the vegetative nucleus. Plastid inheritance appears to be strictly maternal since the sperm cells do not contain plastids; plastids are excluded from the generative cell even in the first mitosis.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Sexual plant reproduction 4 (1991), S. 145-154 
    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
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  • 7
    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
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  • 8
    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
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  • 9
    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
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Protoplasma 140 (1987), S. 141-150 
    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
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