ANTAGONISTIC EFFECTS OF ABSCISIC-ACID AND GIBBERELLIC-ACID ON THE BREAKING OF DORMANCY OF FAGUS-SYLVATICA SEEDS

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 t o endogenous factors. Seed coat removal accelerates both the release f rom dormancy and the effects of the other treatments that abolish it. The dormancy of these seeds is eliminated by cold treatment at 4 degre es C over a period longer than 8 weeks, and exogenous application of a bscisic acid (ABA) reverses the effects of low temperature, the seeds remaining in an ungerminated state. Additionally, ABA reduces protein synthesis bur slightly increases RNA synthesis, which suggests its inv olvement in the synthesis of RNAs related to this process. In vitro tr anslation of the RNAs isolated from these seeds shows that ABA delays the disappearance of at least 2 polypeptides (of ca 22 and 24 kDa), wh ich are abundant in dormant seeds and under conditions that prevent th e release from dormancy, but which disappear under treatments that abo lish it. Exogenous application of gibberellic acid (GA(3)) proved to b e efficient in breaking the dormancy of these seeds and in substitutin g 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 dis appearance of the two polypeptides abundant in dormant seeds and in AB A-treated seeds. These findings suggest that both ABA and GA(3) could be involved in the regulation of nucleic acid and protein metabolism d uring dormancy, acting antagonistically in these processes and, specif ically, in the regulation of the synthesis of the two proteins that ap pear to play a role in the maintenance of dormancy in these seeds.