CELL-CYCLE REACTIVATION IN CULTURED PEA EMBRYO AXES - EFFECT OF ABSCISIC-ACID

We used cultured pea embryo axes to study the effect of exogenous absc isic acid (ABA) on the reactivation of cell proliferation at germinati on. ABA (100 muM) was administered in a complete medium or in a medium without KNO3 (the main source of K+ in the complete medium). In the p resence of ABA, only a few meristematic root tip nuclei progressed thr ough the cell cycle during the first 24 h of germination. Compared to the control the percentage of G0/G1 cells remained high. In the absenc e of KNO3, the inhibitory effect of ABA on the cell cycle increased an d the transition from G1 to S was almost completely inhibited after 24 h of germination. Moreover, the amount of a 47 kDa nuclear protein re mained high in embryos treated with ABA whereas it decreased in the co ntrol.