The best-known examples are the spindle and phragmoplast, but similar constructions can be seen in other phases such as the early bipolar axial microtubule systems associated with the dividing plastids (Fig.
Similar BMAs contribute to the development of complex phragmoplast systems (Fig.
Even though meiotic cytokinesis is delayed until after second division when it occurs simultaneously, a well-developed phragmoplast is typically organized in the equatorial region during anaphase/telophase I.
The mechanism of intracellular motility involved in OB development is not at all understood, especially since the organelles first appear to form a collar surrounding the interzone and then proceed to invade the region at right angles to the BMAs making up the phragmoplast. An interesting variation occurs in Equisetum where the plastids and mitochondria form distinct layers in the OB (Bednara & Rodkiewicz, 1984; Bednara et al., 1986).
Microtubules emanating from the nuclei give rise to a well-developed phragmoplast in the interzone (Fig.
29a-c) and give rise to a phragmoplast in which forms a free-floating disc.
Interaction of opposing sets of microtubules in the interzone gradually gives rise to a well-defined phragmoplast (Fig.
Following chromosome separation in first meiosis, a well-developed phragmoplast begins as a bipolar array in the interzone (Fig.
Immediately a distinctive phragmoplast develops (Fig.
While vesicles and ER fragments are thought to be transported to the forming cell plate by the phragmoplast, it is not at all clear how large organelles such as oil bodies and mitochondria move into the equatorial plane, especially as the movement appears to be at fight angles to the orientation of the phragmoplast microtubules.
Microtubules emanating from proximal surfaces of the nuclei and flanking plastids form a phragmoplast array (Fig.
or spindle microtubules were seen in