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  • 1
    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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  • 2
    ISSN: 1432-2145
    Keywords: Female germ unit ; Nicotiana ; Megagametophyte ; Organelle movement ; Video microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Living embryo sacs and megagametophytic cells of Nicotiana alata and Nicotiana tabacum were obtained using enzymatic maceration and microdissection. The yields of isolated embryo sacs, egg apparatus and central cells were up to 35%, 40% and 35%, respectively. Vectorial movement of organelles and undulations of tubular structures, presumably endoplasmic reticulum, were observed in eggs, synergids and central cells using video-enhanced microscopy. Despite evident viability using the fluorochromatic reaction, the egg displays much less organelle movement and therefore appears to be quiescent. The large vacuole of the central cell is traversed by mobile strands of cytoplasm through which organelles migrate. A polygonal network is located at the periphery of the central cell, which may contribute to anchorage of the cell with the embryo-sac wall. The observation of organelle movement provides direct evidence of the condition of the cell and may be a useful approach for assessing cell vigor.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-2048
    Keywords: Electrical potential changes ; Lignin ; Lilium ; Pistil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cells with secondary wall thickenings are present in the style of Lilium longiflorum Thunb. cv. Arai 5. These cells are located just outside the three vascular bundles radial to the protophloem. The cells are not present everywhere but occur “at random” along the three vascular bundles. They are surrounded by small elongated parenchyma cells. The secondary wall is lignified but their lignification is less than that of the xylem cells. A relationship has been demonstrated between the presence of these cells and the registration of bioelectric potential changes.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 68 (1984), S. 396-396 
    ISSN: 1432-2242
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Sexual plant reproduction 5 (1992), S. 64-71 
    ISSN: 1432-2145
    Keywords: Generative cell ; Isolation ; Microtubules ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Upon squashing of the pollen grain, the isolated generative cell ofNicotiana tabacum looses its spindle shape to become spherical; this phenomenon is independent of the sucrose concentration used. The time necessary for this change can vary from 1 min (0% sucrose) to 20 min (30% sucrose). The microtubular cytoskeleton was studied by means of immunofluorescence and electron microscopy. Just after isolation, 5 to 15 clearly visible bundles in microtubules organized in a basket-like structure are present. After 15 min in medium with 15% sucrose, the microtubular cytoskeleton disappears, and a diffusely spread tubulin can be observed. Neither the addition of 10–20 μM taxol to the medium, nor the omission of Ca2+ to the medium has any effect on the changes in cell shape and loss of microtubular bundles after isolation.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 71 (1985), S. 359-360 
    ISSN: 1432-2242
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1615-6102
    Keywords: Coffea ; in vitro culture ; Embryoids ; Structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The development of embryoids on punched leaf expiants fromCoffea canephora was studied. Both culture conditions as well as structural changes were investigated. The expiants were placed on a modified Murashige and Skoog medium with different concentrations of KNO3. It was found that an increased amount of KNO3 did not raise the rate of embryoid formation. After an initial callus phase embryoids developed on the edges of the punched leaf discs. First embryoids appeared after 37 days in culture. Microscopical examination showed that they arised from clusters of small, plasma-rich cells, situated at the periphery of the callus mass. Because of the small width of the suspensors the embryoids most likely originated from single cells which, however, may be part of a larger proembryonal cell complex.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1615-6102
    Keywords: Tobacco ; Pollen tube ; Organelle distribution ; Endocytosis ; Exocytosis ; Cell wall
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The present study provides the first quantitative analysis on the distribution of organelles in pollen tubes ofNicotiana tabacum L. Organelles were studied on living pollen tubes by means of fluorescence confocal laser scanning microscopy and on cryo-fixed, freeze-substituted and serially sectioned material by electron microscopy. In the tip a 300 nm to 400 nm thick wall was secreted that proximately gradually separated into a wall with an opaque inner side and a more translucent, layered outer side. Tubular endoplasmic reticulum was particularly abundant in the tip of the tube, surrounding the region where secretory vesicles (SV) accumulated. Mitochondria were randomly distributed throughout the cytoplasm, no accumulations were present. Dictyosomes, however, showed an increased abundance at 25–30 μm behind the tip. The accumulation of coated pits (CP) in a zone 6–15 μm behind the tip identifies this zone as the major site of endocytosis: 50% of all CP occur in this zone. Quantification of exo- and endocytosis showed that only part of the membrane material of the SV can be retrieved after exocytosis. The typical zonation in endocytotic activity may serve to maintain a difference in membrane protein composition between the tip and the tube.
    Type of Medium: Electronic Resource
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  • 9
    Publication Date: 1982-12-01
    Print ISSN: 0032-0935
    Electronic ISSN: 1432-2048
    Topics: Biology
    Published by Springer
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  • 10
    Publication Date: 1979-04-11
    Description: This paper is a summary of the Second Bat-Sheva Seminar on magnetohydrodynamic (MHD) Flows and turbulence. It was held in the University of the Negev, Israel, on 28-31 March 1978, with 64 participants from 7 countries. Reviews and research papers were presented on the general theory of MHD, MHD duct flows (with emphasis on novel aspects such as non-uniform fields and fluid properties, bends, free-surface effects and longitudinal diffusion), two-phase flows (especially those likely to occur in a liquid-metal generator), turbulence and instabilities, and electrically driven flows (with new results presented for the theory of laminar and turbulent flows in induction furnaces, and for the theory of thermo-electrically driven flows in transverse magnetic fields). One day of the conference was devoted to turbulence, mainly without magnetic fields, with reviews and new results presented on the theory and measurements of coherent structures, intermittency at high Reynolds number, methods of calculating shear flows, and measurement techniques. The seminar was a strange mixture of people and topics, which produced some interesting papers and some useful discussion. © 1979, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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