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  • 1970-1974  (6)
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Material
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Year
  • 1
    Electronic Resource
    Electronic Resource
    Some ultrastructural features of Volvox, with particular reference to the phenomenon of inversion (1970)
    Springer
    Planta 90 (1970), S. 174-190 
    Details
    ISSN: 1432-2048
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Some features of the ultrastructure of Volvox are described. Golgi bodies were often associated with the endoplasmic reticulum (ER), and the two basal bodies appeared to be accompanied by two probasal bodies. A few vegetative cells were binucleate. All cells examined had a peripheral cytoskeleton of microtubules which was particularly well developed in the cells of sperm packets. During inversion of a colony, the cells elongated considerably, possibly due to the increased length of these peripheral microtubules; the cell profile also became some-what narrowed at the inner edge of the flexing colony. Cytoplasmic connections were large and numerous in young coenobia, but were generally absent in older vegetative colonies; by inversion, they had become confined to the chloroplast end of the cells where they seemed to act as hinges. Elements of the ER ran through these interconnections, possibly providing an intercellular communication network needed for the coordinated activity of inversion. A new structural feature was discovered in the form of circular (or possibly spiral) striations on the plasmalemma around these cytoplasmic connections. They were detectable just before inversion, and were most pronounced immediately after.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00388045
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    “Bristly” cristae in algal mitochondria (1971)
    Springer
    Planta 100 (1971), S. 357-359 
    Details
    ISSN: 1432-2048
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In forming zoospores of Oedogonium, mitochondria were found to contain numerous, evenly-spaced bristle-like structures projecting from the surface of cristae.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00385200
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Mitosis and autospore formation in the green algaKirchneriella lunaris (1970)
    Springer
    Protoplasma 70 (1970), S. 325-347 
    Details
    ISSN: 1615-6102
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Asexual reproduction inKirchneriella lunaris involves autospore formation. After an initial mitosis, the curved cell cleaves to a variable extent, and then the nuclei divide again; finally the cytoplasm is partitioned into four around each nucleus. Rudimentary centrioles appear prior to the first mitosis; centriole complexes then become associated with a developing sheath of extranuclear microtubules at prophase; fenestrae appear at the poles through which both microtubules and centrioles migrate, preceding intranuclear spindle formation. The nucleus meanwhile is enveloped by a perinuclear layer of endoplasmic reticulum which is also interposed between the golgi body and nuclear envelope. Chromosome separation is accompanied by considerable spindle elongation. Finally the reforming nuclear envelope excludes both centriole complex and interzonal spindle apparatus from daughter nuclei. Cleavage is preceded by i) nuclear movement to the cell center, ii) movement of centriole complexes around daughter nuclei until they are opposite one another, and iii) the concurrent formation of a system of transverse microtubules extending across the cell. Other microtubules encircle the cell predicting the cleavage plane. A septum then appears amongst these cytokinetic microtubules, possibly derived from the plasmalemma; it extends across the cell too, through the cleaving peripheral chloroplast. Secondary mitoses follow (as above) during which this septum may be partially resorbed. Finally this septum is reformed, if necessary, and two other septa appear (as above) to quadripartition the cell. Mitotic and cytokinetic structures in this algae are briefly compared with some others.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01275761
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Reproduction by zoospores inOedogonium (1972)
    Springer
    Protoplasma 74 (1972), S. 149-167 
    Details
    ISSN: 1615-6102
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Emergence of zoospores ofOedogonium and their subsequent developmental changes have been studied using live material and sections prepared for light and electron microscopy. Release commences with rupture of the cell wall at its pre-weakened site near the apical caps. The pliable protoplast of the zoospore becomes completely spherical once free of the wall; it is enclosed within the hyaline vesicle which expands continuously and then disappears. Meanwhile, as the flagella become active, the zoospore begins to elongate and its dome starts to protrude from a circular constriction where the flagella are inserted. Once free of the hyaline vesicle, it is actively motile for a variable period, during which elongation continues. The motile phase ceases when the zoospore begins to vibrate, whereupon the flagella are all violently shed. Soon after this, the constriction disappears from around the dome which becomes more pointed; the immobile cell now elongates further, increasing in volume. The cell periphery contains numerous contractile vacuoles. Zoospore elongation may be associated with a proliferation of longitudinal microtubules, and once the flagella are shed, the flagellar rootlet system disintegrates, probably releasing the rootlet microtubules. Mechanisms involved in the release of the zoospore are also discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01279207
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  • 5
    Electronic Resource
    Electronic Resource
    Reproduction by zoospores inOedogonium (1972)
    Springer
    Protoplasma 74 (1972), S. 169-193 
    Details
    ISSN: 1615-6102
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Differentiation of immobile zoospores into future basal cells of vegetative filaments ofOedogonium is described. Once flagella are shed, the constriction disappears from around the dome which soon starts pushing out rhizoid(s); these may become long and/or numerous if cells cannot attach themselves to a substrate. The flagellar apparatus, including the basal bodies, slowly disintegrates within the dome without involving lysosomal structures. A wall is secreted around the elongating cell; several distinguishable types of vesicular components are discharged into it at the dome. Some are derived from hypertrophied golgi bodies, and others from the numerous basal particles (characteristic of zoospores) which had undergone changes in appearance and cytochemical reactivity. The growing rhizoids flatten and extend, finger-like, across the surface of flat substrates, or wrap around vegetative filaments of other alga. The thick holdfats wall is secreted around them, usually forming a structure like a flattened cone; meanwhile the holdfast's interior containing much endoplasmic reticulum becomes increasingly subdivided into a labyrinth by ingrowing folds of wall. Microtubules and extensive arrays of smooth reticulate membranes are present near these walls. The hypertrophied golgi bodies in the holdfast soon revert to their usual smaller size. Eyespots degenerate, and the apical wall develops the circumferential discontinuity which will be the site of the future ring. In unattached germlings, the large accumulation of rough endoplasmic reticulum in the holdfast often shows evidence of breakdown, being replaced by masses of smooth membranes or else homogeneous “souplike” cytoplasm devoid of membranes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01279208
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Reproduction by zoospores inOedogonium (1972)
    Springer
    Protoplasma 74 (1972), S. 195-212 
    Details
    ISSN: 1615-6102
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Cell division in germlings and young filaments ofOedogonium is described. In one species, division proceeded as expected. The ring was formed at the apical wall weakening, and the basal cell did not divide again; the cap of wall derived from the basal cell was sometimes incorporated into the wall of the new apical cell. The second species showed significant differences. The “ring” laid down in the single-celled germling, and sometimes in the apical cell of a two-celled filament covered the whole apical end wall; the basal cell also usually underwent one more division, utilizing a normal ring. It is suggested that the formation of rings for cell division represents an adaptation of a wound-response mechanism, brought into action by the deliberate creation of the circumferential weakening in the apical cell wall, and a concurrent increase in cell turgor. This proposal helps explain the divergent results above, and is further supported by the following examples, given in the paper: a) the frequent occurrence of accidental breaks in the wall, repaired sequentially by the deposition of amorphous and then layered wall material; b) a similar localized wall reinforcement invoked by the presence of rhizoids of other holdfasts attaching themselves to vegetative cells; c) a continuous layer of ring material being deposited over the entire end wall of a dividing cell, when the adjacent apical cell was empty; and d) the deposition of two rings in cells that had been previously treated with colchicine to prevent cytokinesis, and then been allowed to divide again.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01279209
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    Paper (German National Licenses)
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