Hormonal Control of Flower Bud Dormancy in Sour Cherry (Prunus cerasus L.). II. Levels of Abscisic Acid and its Water Soluble Complex1

Abstract

Levels of both free abscisic acid (ABA) and its soluble complex, assumed to be the l’-glucose ester (“bound” ABA), were measured by electron-capture gas-liquid chromatography in the scales and floral primordia of sour cherry. On a per bud basis, more ABA was found in the scales than in the primordia, although the concentration was greater in the primordia. Concentrations of bound ABA were greater than those of free ABA. The concentration of free ABA changed more dramatically in the primordia than in the scales, rising rapidly in the fall, reaching a maximum in Nov. or Dec., then declining rapidly (ca. 4 wk) to or below the original level. The autumn increase was coincident, not with the onset of dormancy, but with the onset of leaf abscission, maximum levels occurring when about 90 to 95% of the leaves had abscised. In addition, free ABA returned to its original level several weeks prior to the termination of rest. Levels of bound ABA paralleled those of free ABA, but declined more slowly during early winter.