Abstract
Colchicine at the concentration of 10-4 M completely inhibited phragmoplast formation of culcured carrot cells and produced large spherical cells, whereas griseofulvin and caffeine produced large but irregular cells. In the presence of griseofulvin or a lower concentration of colchicine (10-5 M), septum formation was incomplete and highly irregular cross walls were formed. Caffeine also inhibited normal septum formation, but it did not induce intricate cross walls.
Inhibition of cytokinesis by 10-4 M colchicine could be the result of the loss of cytoplasmic microtubules in the phragmoplast region. In cells treated with 10-5 M colchicine or 5 × 10-5-10-3 M griseofulvin, a considerable number of microtubules remained but the array of vesicles in the phragmoplast region was markedly disordered. Caffeine seemed to inhibit fusion of the vesicles aligned in the phragmoplast region.
