Lack of Inhibiting Effects of Abscisic Acid on Seeds ofHaplopappus gracilis(Nutt.) Gray Pregerminated in Water for Short Times

Abstract

Abscisic acid (ABA) inhibits germination of Haplopappus gracilis seeds. If seeds are germinated in water until radicle protrusion and then transferred to ABA, no inhibiting effect is observed and growth goes on normally. The same behaviour is observed if embryos (i.e. seeds deprived of coats) are pregerminated in water for 12 h. No growth substance (cytokinins or gibberellins) is able to reverse in short times the inhibiting effects of ABA on germination and on resumption of DNA synthesis; hence it is unlikely that some growth regulator synthesized during the early hours of germination can account for a subsequent neutralization of the inhibiting effects of ABA. It is suggested that ABA is metabolized to some compound devoid of hormonal activity in the seeds during the incubation in water.