ENDOGENOUS IAA LEVELS AND DEVELOPMENT OF COFFEE FLOWER BUDS FROM DORMANCY TO ANTHESIS

Dormant coffee (Coffea arabica L.) flower buds require water stress to stimulate regrowth. A xylem specific water-soluble dye, azosulfamide, was used to quantify water uptake of buds after their release from do rmancy by water stress. In non-stressed flower buds, the rate of water uptake was generally slower and variable compared to stressed flower buds, where the rate of uptake tripled from 1 to 3 days after rewateri ng and preceded the doubling of fresh and dry weight of buds. Free, es ter and amide IAA levels of developing flower buds were measured by ga s chromatography-mass spectrometry- selective ion monitoring using an isotope dilution technique with [C-13(6)]IAA as an internal standard. Throughout development, the majority of IAA was present as amide IAA. The proportions of amide and free IAA increased one day after plants w ere released from water stress, and preceded the doubling of fresh and dry weight. Free and conjugated IAA content per bud remained stable d uring the period of rapid flower growth until one day before anthesis.