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- Title
Cytophysiological studies on Micrasterias I. Nuclear and Cell Division.
- Authors
Waris, Harry
- Abstract
The in vivo observation of nuclear division is possible in Micrasterias rotata, M. Thomasiana, M. angulosa, and M. radiata, in the different species to a varying extent. In the three first-named species with a multiple nucleolus, the approaching division is indicated by the nucleolus resolving itself into groups of distinct granules which are usually first very fine and some what irregular, the »cloud stage», later owing to dissolving and fusing larger and globular, the groups then resembling clusters of grapes, the »grape stage». The granular stage corresponds to the prophase, the »grape stage» representing at least the later part of it. The »grape stage» may last in M. Thomasiana from half an hour to four hours, in M. rotata from half a minute to ten minutes. It ends with a sudden mobilisation of the granules, the »nucleolar mobilisation», which signifies the beginning of spindle formation and can be determined, in suitable eases, with a precision of some seconds. In M. radiata, which possesses a single nucleolus, the approaching division is indicated by the edge of the nucleolus becoming uneven, as if granulated, before the nucleolus gradually disappears. Also in this case a movement of the nucleolus may sometimes be observed. The chromosome number is in M. Thomasiana about 34–38, in M. angulosa 60–64, in M. rotata about 200. In M. Thomasiana and M. rotata two of the cbromosomes are especially conspicuous owing to their length. In M. Thomasiana both the long chromosomes show an unstained portion near one end and posses a trabant. The original number of nucleoli appearing in the young daughter-nuclei in M. Thomasiana and M. rotata is often two. Even in M. radiata two nucleoli, a large and a small one, may sometimes be observed in the young daughter-nuclei. The movements of chromosomes during metaphase and anaphase can be observed in the rotata, during anaphase in M. radiata and less distinctly in M. angulosa. The metaphase plate can be distinguished in all four species investigated, less distinctly in M. Thomasinia. The speed of anaphase movement at room temperature was estimated in M. rotata and M. angulosa at about 2 μ per minute, in M. radiata at 4.6 μ per minute.
- Subjects
MICRASTERIAS; DESMIDIACEAE; ZYGNEMATALES; GREEN algae; CNIDARIA; INVERTEBRATES
- Publication
Physiologia Plantarum, 1950, Vol 3, Issue 1, p1
- ISSN
0031-9317
- Publication type
Article
- DOI
10.1111/j.1399-3054.1950.tb07487.x