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  • Allium cepa L  (2)
  • Replication rate  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Immediate disruption of spindle poles and induction of additional microtubule-organizing centres by a phenylcarbamate, during plant mitosis (1998)
    Springer
    Protoplasma 204 (1998), S. 119-127 
    Details
    ISSN: 1615-6102
    Keywords: Phenylcarbamates ; Multipolar spindles ; Microtubule-organizing centres ; Aneuploidy ; Allium cepa L
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The herbicide carbetamide [(R)-1-(ethylcarbamoyl) ethylphenylcarbamate], in the 0.4 to 0.8 mM range, efficiently induced multipolar mitoses inAllium cepa L. The frequency of multipolar anaphases rose earlier and reached higher values when both concentration and time of treatment increased, up to a maximum of 90% after 1 h of treatment. To identify the physiological target, the kinetics of induction of multipolar mitoses were followed during recovery from very short treatments (5, 10, and 15 min). Tubulin immunodetection showed that phenylcarbamate immediately disrupts the cohesion between the different bundles of microtubule minus ends which converge at the pole. The spindle was rendered multipolar about three times more efficiently in metaphase than in anaphase. The observations do not support any effect of the herbicide on the tubulin polymerization-depolymerization cycle, and suggest that the minus ends of the microtubules remained stabilized in carbetamide. Thus, the density of kinetochore microtubules and their lengths were unmodified in the individual chromosomes which became detached from both spindle poles in response to the herbicide. Extra microtubule-organizing centres for the assembly of both preprophase band and phragmoplast (the tubulin arrays which characterize the microtubular cycle responsible for cytokinesis in plant cells) were also rapidly induced.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01280318
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Selective hypoxic depression of late replication in meristematic cells ofAllium cepa (1992)
    Springer
    Protoplasma 168 (1992), S. 1-6 
    Details
    ISSN: 1615-6102
    Keywords: Replication rate ; Hypoxia ; Meristems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Under hypoxia (10 and 5% partial oxygen tension) meristematic cells ofAllium cepa L. roots acquired new cycle kinetics, characterized by reduced but constant rates of root growth. Under these conditions, there was preferential lengthening of G1 and of the last third of the S period, S3. Since hyperoxygenation shortened S3 but not G1 in these cells, the high sensitivity of late replication to environmental oxygen is demonstrated. The preferential depression of the replication rate when those cells replicated the last third of their DNA was not associated with diminished cell size. Rather, the lower the oxygen level the larger the mean size of the cycling cells. Under anoxia (0% oxygen tension) the rate of growth slowed, accompanied by preferential accumulation of cells in G1. However, steady state kinetics of root growth was not achieved under these extreme conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01332644
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Microtubular structures developed in response to a carbamate herbicide in plant mitosis (1997)
    Springer
    Protoplasma 200 (1997), S. 65-70 
    Details
    ISSN: 1615-6102
    Keywords: Carbamates ; Microtubules ; Mitosis ; Cytokinesis ; Caffeine ; Allium cepa L
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Indirect immunodetection of tubulin showed that the herbicide carbetamide activated silent signals left by the preprophase band (PPB) and by old phragmoplasts. Thus, after half an hour of treatment, 5.3% of anaphases inAllium cepa L. meristems showed spindle microtubules pointing to sites of the longitudinal cell membranes which, under control conditions, would only start attracting microtubules from the growing phragmoplast at late telophase. After 2 h, 12.8% of the telophases showed not only the expected phragmoplast between the two sister nuclei, but one or two additional phragmoplasts, at one or both cell tips, the sites of the phragmoplasts from the telophases of previous cycles. A few binucleate cells, obtained by aborting phragmoplast formation by a short caffeine treatment, developed three phragmoplasts in their next mitosis (bimitosis) in the presence of carbetamide: one between each sister pair of telophasic nuclei plus an extra one. The latter also occupied the site of the phragmoplast of the telophase of the previous cycle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01280735
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    Paper (German National Licenses)
    Fulltext
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