REGULATION OF ABA LEVELS IN SENESCING PETALS OF ROSE FLOWERS

During the vase life of a rose flower, changes in the levels of abscisic acid (ABA) were observed: a decrease during the first 3 days, followed by a steady state at a low level, and finally a sharp increase in late senescence. Feeding [2-C-14]ABA to isolated petals showed that metabolism was very active despite the age of the flower, oxidation processes increased with age, whereas conjugation decreased but the level of nonmetabolized ABA remained stable. When the isolated petal was subjected to water stress, whatever its age, the ABA level increased. Hydrolysis of ABA-GE was not involved in this phenomenon. Thus, ABA synthesis occurred in the isolated petal; it could be directly correlated to the decrease in water potential However, the ABA increase in isolated petals was limited. Moreover, on the rose tree, increases in ABA levels were not correlated to water potential changes. ABA levels seemed, therefore, mainly regulated by changes in import from leaves and other parts of the flower.