[Prometaphase aberrations leading to the nuclei restitution].

The mechanism of restitution nuclei formation in male meoiosis of Triticum-Agropyrum F1 hybrid and monosomic wheat line Milturum 553 has been studied. Visualization of division spindle with Navashin's routine fixationle distribution method accompanied with acetocarmine-coloured squashed preparations revealed that a block in the kinetochore spindle thread formation, i.e. the absence of chromosome association with the division spindle, is the basic reason of restitution in these genotypes. On this background, the prometaphase spindle in abnormal meiosis of these lines demonstrates a number of vivid and inordinate aberrations revealing some regularities of spindle structure in the normal plant cell.