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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Protoplasma 126 (1985), S. 47-53 
    ISSN: 1615-6102
    Keywords: Nucleolar cycle ; Allium cepa L. ; Hypoxia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Hypoxia disturbs the nucleolar cycle inAllium cepa L. meristems by diminishing the disorganizing stage and increasing the nucleologenesis time. Though nucleolar remnants persist in the enlarged metaphase recorded under hypoxia, prenucleolar bodies appear at the same time than in control meristems if related to the timing of nucleolar envelope breakage. Such appearance is apparently independent of the chromosome condensation cycle, since it took place in anaphase and not in midtelophase as in controls. Finally, the involvement of NORs in segregation is questioned since prenucleolar bodies are also segregated under hypoxia, both when integrated in the reforming nuclei or when dispersed in cytoplasm.
    Type of Medium: Electronic Resource
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  • 2
    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
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