Endogenous Cytokinins and Lateral Bud Growth in Roses

The levels of endogenous cytokinins were determined in the buds of rose plants (Rosa hybrida `Golden Times') in nondecapitated controls and after decapitation. Contrary to expectations, we found that buds lower down the stem, which were subject to correlative inhibition, contained higher levels of cytokinin than upper, less inhibited buds. With the resumption of growth, the endogenous cytokinins increased in the developing upper axillary shoots while they decreased in the lower buds, which then became less inhibited The present evidence suggests that the role of cytokinins in apical dominance must be reassessed. We suggest that low rather than high levels of endogenous cytokinins are indicative of the ability of axillary buds to resume growth The low levels of cytokinins may indicate that they are utilized within the buds and that this may program the buds for rapid development.