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  • 1965-1969  (2)
  • 1935-1939
  • 1968  (2)
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  • 1965-1969  (2)
  • 1935-1939
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  • 1
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract In binucleate 2n-2n and 4n-4n, trinucleate 2n-4n-2n and tetra nucleate cells 2n-2n-2n-2n which had been experimentally induced by means of caffeine (0.1% in tap water) in root-tip cells of onion bulbs (Allium cepa) division cycle time increases sligthly (about 15%) when the DNA content increases from 2n to 8n chromosomes per cell. The interphase time is not significantly modified, whereas the mitosis time increases (about 50%) in the tetranucleate cells in relation to the diploid mononucleate cells. The unsynchronized initiation of prophase and the subsequent synchronization of the nuclei in the polynucleate cells suggest an inhibiting mechanism regulating initiation of the mitosis via cytoplasm.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1615-6102
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The study of the cell division cycle by means of caffeine labelling inAllium roots, at 15° C, employing intact root and decapitated roots at several levels (0.5, 1.0, 1.5, 2.0, and 2.5 mm) has shown that the number of cycles developed by the cells is constant at each meristem level. This number and the durations of the cycles are not affected by the decapitation. It is suggested that the cell cycle is controlled in the meristematic cells by an intracellular programme which would be developed throughout the meristem. However, the larger the region decapitated is, the more decreases the growth rate of the roots. The removal of the root cap (about 0.5 mm) did not modify the rate of root growth, although it blocked the geotropic response. The quiescent center is proposed as a source of auxin controlling cell elongation.
    Type of Medium: Electronic Resource
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