Heteromorphism of stamens in monoclinous flowers of Tinantia erecta (Jacq.) Fenzl as an example of high variability of the androecium in the Commelinaceae family.

Representatives of the family Commelinaceae are characterised by morphologically, anatomically, or functionally diverse stamens (common presence of staminodia), which produce diverse pollen grains. The heteromorphism of stamens noted in all Commelinaceae species is a particular example of the evolutionary modification of the androecium in entomophilous plants. The morphological, anatomical, and cytological analyses of the androecium as well as the analysis of the microsporogenesis process and the formation of the male gametophyte in Tinantia erecta (a species belonging to the family Commelinaceae) have demonstrated that the morphologically diverse stamens in this species do not differ anatomically. Furthermore, the process of microsporogenesis followed by gametogenesis occurring in the stamens yields pollen grains with the same morphology, cytology, and function. Therefore, despite the large morphological diversity of the androecium, all anthers in T. erecta produce male gametophytes that are identical in every respect, which is a unique feature in species from the Commelinaceae family. Additionally, T. erecta is capable of self-pollination; hence, it can be claimed that the species uses its entire reproductive potential to produce seeds and a next generation.

A new type of microtubular cytoskeleton in microsporogenesis of Lavatera thuringiaca L.

In Lavatera thuringiaca, kariokinesis and simultaneous cytokinesis during the meiotic division of microsporogenesis follow a procedure similar to that which takes place in the majority of members of the class Angiospermae. However, chondriokinesis occurs in a unique way found only in species from the family Malvaceae. Chondriokinesis in such species is well documented, but the relationship between the tubulin cytoskeleton and rearrangement of cell organelles during meiosis in L. thuringiaca has not been precisely defined so far. In this study, the microtubular cytoskeleton was investigated in dividing microsporocytes of L. thuringiaca by immunofluorescence. The meiotic stages and positions of cell organelles were identified by staining with 4',6-diamidino-2-phenylindole. We observed that, during prophase I and II, changes in microtubular cytoskeleton configurations have unique features, which have not been described for other plant species. At the end of prophase I, organelles (mostly plastids and mitochondria) form a compact envelope around the nucleus, and the subsequent phases of kariokinesis take place within this arrangement. At this point of cell division, microtubules surround the organelle envelope and separate it from the peripheral cytoplasm, which is devoid of plastids and mitochondria. In telophase I, two newly formed nuclei are tightly surrounded by the cell organelle envelopes, and these are separated by the phragmoplast. Later, when the phragmoplast disappears, cell organelles still surround the nuclei but also move a little, starting to occupy the place of the disappearing phragmoplast. After the breakup of tetrads, the radial microtubule system is well developed, and cell organelles can still be observed as a dense envelope around the nuclei. At a very late stage of sporoderm development, the radial microtubule system disappears, and cell organelles become gradually scattered in the cytoplasm of the microspores. Using colchicines, specific inhibitors of microtubule formation, we investigated the relationship between the tubulin cytoskeleton and the distribution of cell organelles. Our analysis demonstrates that impairment of microtubule organization, which constitutes only a single component of the cytoskeleton, is enough to disturb typical chondriokinesis in L. thuringiaca. This indicates that microtubules (independent of microfilaments) are responsible for the reorganization of cell organelles during meiotic division.