Antagonistic effects of abscisic acid and gibberellic acid on the breaking of dormancy of <i>Fagus sylvatica</i> seeds

Abstract

Study of the factors involved in the dormancy of Fagus sylvatica seeds shows that such dormancy is due partly to the seed coats and partly to endogenous factors. Seed coat removal accelerates both the release from dormancy and the effects of the other treatments that abolish it. The dormancy of these seeds is eliminated by cold treatment at 4°C over a period longer than 8 weeks, and exogenous application of abscisic acid (ABA) reverses the effects of low temperature, the seeds remaining in an ungerminated state. Additionally, ABA reduces protein synthesis but slightly increases RNA synthesis, which suggests its involvement in the synthesis of RNAs related to this process. In vitro translation of the RNAs isolated from these seeds shows that ABA delays the disappearance of at least 2 polypeptides (of ca 22 and 24 kDa), which are abundant in dormant seeds and under conditions that prevent the release from dormancy, but which disappear under treatments that abolish it. Exogenous application of gibberellic acid (GA 3 ) proved to be efficient in breaking the dormancy of these seeds and in substituting for cold treatment as well as in antagonizing the effects of ABA on the synthesis of both DNA and proteins. GA 3 also accelerates the disappearance of the two polypeptides abundant in dormant seeds and in ABA‐treated seeds. These findings suggest that both ABA and GA 3 could be involved in the regulation of nucleic acid and protein metabolism during dormancy, acting antagonistically in these processes and, specifically, in the regulation of the synthesis of the two proteins that appear to play a role in the maintenance of dormancy in these seeds.