Cell division of binuclear cells induced by caffeine: Spindle organization and determination of division plane

Synchronously dividing binuclear cells were induced in root tips ofTriticum turgidum by caffeine treatment. Spindle and other microtubular configurations of such cells were studied using tubulin immunofluorescence and electron microscopy. The binuclear cells developed one, two or three preprophase microtubule bands longitudinally, transversely or rarely in a cross configuration. During the mitotic entry binuclear cells formed prophase spindles separately around each nucleus. When the nuclei were located fairly apart, their spindle structures developed independently throughout all mitotic phases. But when the nuclei were located closely together their metaphase and anaphase spindles shared a common polar region. However, the two spindles in such cells retained their functional autonomy. They display structurally independent minipoles in the common polar region. After anaphase the neighbouring nonsister chromosome groups of nuclei divided by a common polar region come to lie close together and in telophase, become enclosed by a common nuclear envelope. During cytokinesis of binuclear cells cell plates were formed only between sister nuclei. These cell plates may develop normally or may curve or branch giving rise to aberrant daughter cell walls. The peculiar mode of spindle and spindle polar region organization of binuclear cells and determination of the division plane in them are discussed.