Effects of colchicine on cell shape and on microfibril arrangement in the cell wall of Closterium acerosum.

Cell morphogenesis in Closterium acerosum (Schrank) Ehrenberg was greatly influenced by colchicine. Addition of colchicine to the medium led to production of "tadpole-shaped" cells, by decreasing the length and increasing the thickness of the new semicells. Transversely oriented wall microtubules and microfibrils, characteristic of normally elongating semicells, were not observed in colchicine-treated semicells, randomly oriented microfibrils being present instead. About 3.5 h after septum formation, the randomly oriented microfibrils began to be overlaid by bundles of microfibrils as seen in normal semicells at the later stage of elongation. When colchicine treatment was terminated 1 h after septum formation, cell elongation was partially restored and microfibrils were deposited parallel to each other and transversely to the cell axis, indicating that the effect of colchicine on microfibril arrangement in growing semicells is reversible.