COLCHICINE STIMULATION OF INTERPHASE CELLS - TIMING THE RESPONSE USING 5-AMINOURACIL

Roots of Vicia faba were treated with 0.0125% colchicine for 3 h. In the following 8 h mitotic indices increased in primary and lateral roots and in small primordia; it rose to 27.3 in lateral roots. When the colchicine treatment was followed by treatment with 5-aminouracil the increase in M. I. was suppressed; M. I. decreased progressively as the duration of 5-AU treatment was; 1) increased from 3 to 6 and to 8 h and, 2) as the interval between the end of the colchicine treatment and the start of 5-AU treatment was decreased from 5 to 0h. An 8h treatment with 5-AU reduced M. I. in laterals to 1.7; this value is similar to that seen after treatment with 5-AU alone for 6h, i. e. 1.8. Colchicine stimulates cells to complete interphase at an accelerated rate. But since the cells that respond to colchicine are blocked by 5-AU it is concluded that colchicine exerts its effects on cells in G1 (or G0) or the S phase. The results are discussed in terms of heterogeneity of cell cycle duration and how it may be controlled. © 1979, Japan Mendel Society, International Society of Cytology. All rights reserved.