Changes in Abscisic Acid Biosynthesis and Catabolism during Dormancy Breaking in Fagus sylvatica Embryo

Abstract.

At harvest, embryos of Fagus sylvatica are dormant. A cold pretreatment without medium at 30% moisture content allowed them to germinate. A comparison of the abscisic acid (ABA) content before and after the pretreatment has no significant relevance since dormancy is expressed during the culture at 23°C. During this culture, both de novo biosynthesis and conjugate hydrolysis contributed to maintain a high level of ABA in the dormant axis. The level of conjugates and the rate of hydrolysis were not modified substantially by the cold pretreatment. In contrast, the dormancy release was associated with a strong decrease in the capacity for ABA synthesis. Moreover, feeding (+)-[³H]ABA to untreated and pretreated embryos proved that the cold treatment also induced a hastening of ABA catabolism.