ESTABLISHMENT OF SYNCHRONY BY STARVATION AND READDITION OF AUXIN IN SUSPENSION-CULTURES OF CATHARANTHUS-ROSEUS CELLS

A system of synchronous cell division was established by starvation of auxin and its readdition to suspension cultures of cells of Catharanthus roseus L. cv. Little-Pinky. When cells in the stationary phase were transferred to fresh medium free of 2,4-dichlorophenoxyacetic acid (2,4-D), cells were arrested preferentially at the G1 phase. After cells had been cultured for 2 days in medium without 2,4-D, readdition of 2,4-D induced the synchronous division of cells. In this system, 70-80% of cells divided synchronously within 3 to 4h, and the mitotic index increased sharply in parallel with the increase in cell number. Active synthesis of DNA was demonstrated by measurements of incorporation of [H-3]-thymidine into the DNA fraction. The induction of cell division by the addition of 2,4-D) inhibited by treating cells with analogues of auxin, such as 2,4,6-trichlorophenoxyacetic acid and p-chlorophenoxyisobutyric acid.