THE EFFECT OF TAXOL ON TRITICUM PREPROPHASE ROOT-CELLS - PREPROPHASE MICROTUBULE BAND ORGANIZATION SEEMS TO DEPEND ON NEW MICROTUBULE ASSEMBLY

To examine whether preprophase microtubule band (PPB) organization occurs by rearrangement of pre-existing, or by assembly of new microtubules (Mts), we treated root cells of Triticum turgidum with taxol, which stabilizes pre-existing Mts by slowing their depolymerization. With taxol early preprophase cells failed to form a normal PPB and PPB narrowing was prevented in cells that had already formed a wide one. The PPB became persistent in prometaphase cells and the formation of multipolar prophase-prometaphase spindles was induced. These data favour the suggestion that PPB formation and narrowing, as well as prophase spindle development, are dynamic processes depending on continuous Mt assembly at the PPB site and in the perinuclear cytoplasm.