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  • 1965-1969  (5)
  • 1935-1939  (1)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 22 (1966), S. 501-502 
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Resumen En los meristemos radicales (en columna) las células hermanas poseen ciclos mitóticos de distinta duration según su positión con respecto al ápice. La célula hermana mâs próxima al ápice posee un ciclo ligeramente más corto que la otra. Se sugiere la existencia de un gradiente de la duration del ciclo desde las células iniciales hasta las células de la región de diferenciación.
    Type of Medium: Electronic Resource
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  • 2
    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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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Archives of toxicology 8 (1937), S. A53 
    ISSN: 1432-0738
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1615-6102
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary This paper reports the results of a study of root growth, the duration of the division cycle and the cell size in onion roots (Allium cepa) at different temperatures (5, 15, 25, 30, and 35° C) and at different oxygen tensions (2, 5, 10, and 20% at 25° C). The growth rate increases with the temperature up to a maximum between 25 and 30° C, while the division cycle shows a minimum duration between 30 and 35° C and the final size of the epidermic cells remains constant from 5 to 25° C decreasing from this temperature onwards. The oxygen tension shows a marked effect in conditioning the root growth. The growth rate increased the slower the nearer the oxygen tension was to the concentration found in the air. The division cycle appears to be strongly dependent on this environmental factor, whereas the final cell size is observed to be constant at all the oxygen tensions tested. There follows a discussion of the effects of the various environmental factors on root growth and on its components, namely cell formation and cell elongation.
    Type of Medium: Electronic Resource
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  • 5
    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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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 75 (1966), S. 591-600 
    ISSN: 1432-0878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Measurement of the B-interphase has afforded a means of calculating the duration of the cell division cycle at various temperatures, from 0° to 40° C, in the root meristems of Allium cepa. For this purpose caffeine labelling was used to produce a small population (1–5%) of highly synchronized binucleate cells. The B-interphase is what we call the period from 0 hour (end of the one-hour caffeine treatment) to the appearance of the first binucleate cells in bi-prophase. The duration of the phases that make up the cycle was calculated from their relative frequency within the meristematic population. Observation shows that at 0° and at 40° the cells do not go through the cycle at all and that from 10° to 30° the speed increases in almost linear proportion. There is no significant change in the relative duration of any of the morphological phases under any of the conditions tested. In discussing these results the authors propose the use of the cell flow (percentage of meristematic cells passing through any point in the cycle in one hour) as an expression in the simplest form of the steady-state kinetics of the meristematic population at a given temperature.
    Type of Medium: Electronic Resource
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