Organelle aggregations during microsporogenesis with simultaneous cytokinesis in species from the family Malvaceae (Gossypium arboreum, Alcea rosea, Lavatera thuringiaca)

During meiosis in microsporogenesis in spermatophytes and in sporogenesis in bryophytes and ferns, regular rearrangement of cytoplasmic organelles (chondriokinesis) occurs. In the present paper, the course of chondriokinesis has been analysed in several representatives of the family Malvaceae (Gossypium arboreum, Alcea rosea and Lavatera thuringiaca). It was revealed that cell organelles in all the species analysed aggregated around the nucleus at the end of prophase I, and next they surrounded two nuclei in telophase I. This position persisted not only until the end of meiosis, but also in post-meiotic cells after formation of microspore sporoderm on mononuclear pollen grains. Currently, this type of cell organelle aggregation has not been reported from other plant groups, and it seems to be characteristic of the representatives of the family Malvaceae only. The role of this type of cell organelle rearrangement still requires elucidation. The current theories are concerned with dividing cells, whereas the cell organelle aggregation described in the present work was observed in post-meiotic cells as well, i.e. in mononuclear pollen grains.