| Abstrakt: |
Summary Changes in plastidome morphology in several definite stages of both the vegetative (asexual) and generative (sexual) life cycle ofPolytoma papillatum were examined by means of serial sectioning technique. Just after completion of cytokinesis daughter cells contain a simple through-shaped, bulky and scarcely perforated leucoplast whose opening faces the original plane of cell cleavage (=lateral part of the new daughter cell). In the course of progressive reorganization the trough-shaped leucoplast is first transformed into a hollow oviform meshwork whose reticulated frame is irregular in shape, size and distribution and whose interior is traversed at the base by two sheets, thus forming separate chambers. This then becomes the typical cup-shaped leucoplast of interphase cells, whose elongated cylindrical lateral part is thin and highly perforated and whose cup-opening faces the apical part of the cell. The changes in leucoplast morphology, probably due to reshuffling and reorganization processes, are correlated to leucoplast areas characterized both by starch and membrane breakdown and by frequent appearance at times of upheaval during leucoplast differentiation. Fusion of two leucoplasts to again form a large, highly perforated cup was also investigated; union of both gametic leucoplasts in such a spherical quadriflagellate zygote is demonstrated by a reconstructed model. Finally the relevancy of these morphological data to extranuclear inheritance is discussed. |
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