CHANGES IN DURATION OF MITOTIC CYCLE INDUCED BY COLCHICINE AND INDOL-3YL-ACETIC ACID IN VICIA FABA ROOTS

Cells of root meristems of Vicia faba were labelled with tritiated thymidine and treated with colchicine or IAA or both. The effects of these compounds on the duration of the mitotic cycle and its constituent phases have been determined using the labelled mitoses wave method of Quastler and Sherman. Colchicine shortens the mitotic cycle of the cells in interphase at the time of treatment; it appears to stimulate cells in G1 or early S to complete interphase faster than untreated cells. The affected cells arrive at mitosis 9-12 h after the beginning of treatment and contribute to the increase in mitotic index seen after treatment with colchicine. Treatment with IAA did not affect cells in G2 but it delayed cells in S; this results in a temporary fall in M.I. The effect of IAA in prolonging interphase was also seen in roots treated with colchicine and IAA; the tetraploid cells induced by colchicine take longer to reach metaphase than cells treated only with colchicine. The results suggest that colchicine and IAA affect different phases of the cell cycle. © 1969 Oxford University Press.