INTERACTION BETWEEN ABSCISIC-ACID AND FUSICOCCIN DURING GERMINATION AND POST-GERMINATIVE GROWTH IN HAPLOPAPPUS-GRACILIS

Abscisic acid (ABA) 10-5 M completely inhibits the germination of seeds of Haplopappus gracilis, and this effect can be effectively reversed by fusicoccin (FC). Nevertheless, when the analysis of reversal promoted by FC is extended to post-germinative growth, it is observed that it results only in a limited elongation of the embryos, perhaps only through cell enlargement, which does not involve any significant resumption of DNA synthesis, cell division or such developmental features as synthesis of chlorophyll and development of root hairs. It is proposed that ABA inhibition of seed germination involves at least two different mechanisms, one mechanism interfering with K+ uptake at the level of the cell membrane, which is reversed by FC, promoting cell elongation, the other interfering with the synthesis of nucleic acids and/or protein synthesis and not being affected by FC. © 1979.