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  • 1
    ISSN: 1432-2048
    Keywords: Bryophytes ; Sporophyte-gametophyte relationships ; Timmiella ; Transfer cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The sporophyte foot of the mossTimmiella barbuloides consists of an unistratose epidermis of transfer cells, a parenchymatous cortex, and a small central strand consisting only of hydroids. The parenchymatous tissue of the vaginula develops one layer of transfer cells opposite the foot, whose lower extremity extends into the gametophyte stem's central strand. From the bottom to the top of the foot the ultrastructure of the sporophyte transfer cells shows some gradual changes that appear related to a functional specialization of these cells. According to a centripetal gradient, the quantity of plastid starch progressively lessens in both vaginula parenchyma and foot cortex. the observed morphological patterns suggest that in the foot-vaginula complex nutrients are translocated radially up to the sporophyte central strand.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Protoplasma 156 (1990), S. 29-38 
    ISSN: 1615-6102
    Keywords: Mitosis ; Moss sporogones ; Monoplastidy ; Mitotic plastid behaviour ; Timmiella ; Bryophyta
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Mitotic cell division of monoplastidic sporogones was investigated in the mossTimmiella barbuloides (Brid.) Moenk. (Pottiales, Bryophyta) by TEM. Division polarity of sporogones is established by the interphase position of the single oblong cup-shaped plastid, which is orientated with its long axis parallel to one of the cell walls. In preprophase the plastid elongates and its extremities bend at right angles. Plastid growth is directed by microtubules and accompanied by plastid tubules. The plastid begins the process of duplication by constricting centrally in the plane of the future cytokinetic septum. There is no preprophase band of microtubules at the division site. The large central nucleus becomes fusiform and aligned parallel to the main plastid axis. By the end of prophase the daughter plastids are positioned at the opposite poles of the nucleus where they probably function as nucleating or organizing centres for the spindle microtubules. Metaphase and anaphase spindles contain long sheets of ER. Cytokinesis involves the formation of a well developed phragmoplast.
    Type of Medium: Electronic Resource
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