Changes in abscisic acid content and embryo sensitivity to (+)-abscisic acid during the termination of dormancy of yellow cedar seeds.

Yellow cedar seeds are dormant at maturity. The abscisic acid (ABA) content of the embryo (but not the megagametophyte) decreased approximately 2-fold following exposure of seeds to a dormancy-breaking treatment; this process was also accompanied by a 10-fold lowered sensitivity of the embryo to S:-(+)-ABA. A decline in ABA within the seed is not sufficient for dormancy breakage; reduced embryo sensitivity to ABA is also required.