| Autor: |
Greuel, Brian T., Floyd, Gary L. |
| Předmět: |
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| Zdroj: |
Journal of Phycology; Sep85, Vol. 21 Issue 3, p358-371, 14p |
| Abstrakt: |
Vegetative cells of Gonium pectorale have a fine structure similar to that of chlamydomonas. In additions three zones comprise an extracellular matrix; a fibrillar sheath and tripartite boundary surrounds the entire colony. Cytokinesis is accomplished by a physcoplast and cleavage furrow. The flagellar apparatus of the immature vegetative cell of this colonial alga is similar to that of Chlamydomonas, but the basal bodies are slightly separated at their proximal ends. The four microtubular rootlets alternate between two and four members. During development, the basal bodies become further separated and nearly parallel. The distal fiber is stretched, but it remains attachment to both basal bodies. At maturity, the basal bodies of peripheral cells of the colony have rotated in opposite directions on their longitudinal axes resulting in a displacement of the distal fiber to one side, an asymmetrical orientation of the rootlets and loss of 180° rotational symmetry. Central cells remain similar to Chlamydomonas in that basal bodies do not rotate, rootlets are cruciate, the distal fiber remains medially inserted and 180° Rotational symmetry is conserved. A 'pin-wheel' configuration of flagellar pairs and the orientation of parallel rootlets toward the colony perimeter probably accounts for the rotation of the colonies during forward swimming. In addition, these ultrastructural features support the traditional placement of G. pectorale as and intermediate between the unicellular Chlamydomonas and the more complex colonial volvocalean genera. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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