CELL-DIVISION OF BINUCLEAR CELLS INDUCED BY CAFFEINE - SPINDLE ORGANIZATION AND DETERMINATION OF DIVISION PLANE

Synchronously dividing binuclear cells were induced in root tips of Tr iticum turgidum by caffeine treatment. Spindle and other microtubular configurations of such cells were studied using tubulin immunofluoresc ence and electron microscopy. The binuclear cells developed one, two o r three preprophase microtubule bands longitudinally, transversely or rarely in a cross configuration, During the mitotic entry binuclear ce lls formed prophase spindles separately around each nucleus, When the nuclei were located fairly apart, their spindle structures developed i ndependently throughout all mitotic phases. But when the nuclei were l ocated 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 mini poles in the common polar region, After anaphase the neighbouring non- sister chromosome groups of nuclei divided by a common polar region co me to lie close together and in telophase, become enclosed by a common nuclear envelope. During cytokinesis of binuclear cells cell plates w ere formed only between sister nuclei, These cell plates may develop n ormally or may curve or branch giving rise to aberrant daughter cell w alls, The peculiar mode of spindle and spindle polar region organizati on of binuclear cells and determination of the division plane in them are discussed.