[Two novel meiotic restitution mechanisms in haploid maize (Zea mays L.)].

Two original mechanisms of nuclear restitution related to different processes of meiotic division of pollen mother cells (PMCs) have been found in male meiosis of the lines of maize haploids no. 2903 and no. 2904.

[Cortical cytoskeletal ring in prophase II leads to correction of abnormalities of the first meiotic division and to meiotic restitution of pollen mother cell nucleus].

The deviation of prophase cytoskeletal ring formation was determined during meiotic division in 50% of pollen mother cells (PMCs) in maize haploid No 1498 (Zea mays). At prophase in both meiotic divisions the cytoskeletal ring is formed in cortical region of cytoplasm instead of perinuclear. Sometimes formation of both perinuclear and cortical rings is observed in the same cell.

[Altering of phragmoplast orientation as a result of excessive centrifugal movement in the absence of cell plate].

The inability of phragmoplast to stop its centrifugal movement after reaching the mother cell membrane is described in abnormal meiosis with the arrest of cell plate formation. The excess of phragmoplast expansion leads to rotation of the whole telophase figure (phragmoplast with daughter nuclei) within the cell through 90 degrees. It has been suggested that this phenomenon may occur because of a the lack of signal stopping cytokinesis.

[Polyarchal spindles in higher plant meiosis].

Morphogenesis and functioning of polyarchal spindles in higher plant meiosis were studied. A mechanism of anastral spindle formation in discussed.

[Consolidation of cytoskeleton during plant spindle formation. I. Abnormalities of spindle integrity in meiosis].

The process of formation of multiple spindles in mononucleate pollen mother cells during meiosis in general wide hybrids F1 and haploids is described. It is assumed that the abnormality may be caused by aberration of a special process at late prometaphase providing for the spindle consolidation.