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

We used cultured pea embryo axes to study the effect of exogenous abscisic acid (ABA) on the reactivation of cell proliferation at germination. 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 presence of ABA, only a few meristematic root tip nuclei progressed through the cell cycle during the first 24 h of germination. Compared to the control the percentage of G0/G1 cells remained high. In the absence of KNO3, the inhibitory effect of ABA on the cell cycle increased and the transition from G1 to S was almost completely inhibited after 24 h of germination. Moreover, the amount of a 47 kDa nuclear protein remained high in embryos treated with ABA whereas it decreased in the control.