Abstract
Individual flowers from Rhododendron L. ‘Prize’ inflorescences were used at various stages of development for quantitative analysis of endogenous free abscisic acid (ABA) content by gas-liquid chromatography with electron capture detection. A decrease of endogenous ABA levels was observed in bud scale, petal, and gynoecium tissue during 6 weeks of cold treatment (9°C) given for release of floral bud dormancy. However, plants which received no cold treatment flowered as rapidly as plants exposed to 6 weeks of 9°. Therefore, a relationship between endogenous ABA levels and the capacity of azalea floral buds for continued development after a cold treatment could not be shown. Regression models of endogenous ABA content on respective morphological measurements of flower bud parts were computed to illustrate the relationship between destructive hormonal determinations and defined morphological changes over time.