The Effect of Hadacidin on Bud Development and its Implications for Apical Dominance

Hadacidin, which is known to inhibit the enzyme adenylo-succinate synthetase, was applied locally to lateral buds on decapitated Pisum sativum L. plants. In controls the buds grew out normally, but the treated buds were almost completely inhibited. After a delay, the buds overcame the inhibition, and their subsequent outgrowth could be further hastened by the local application of a cytokinin. The inhibition, unlike that due to IAA, was not transported to a second bud, and it could be largely reversed by kinetin or dimethylallylaminopurine. Adenine itself produces little or no reversal, however. There was some reversal by aspartic acid, which is known to reverse, at least partially, the hadacidin inhibition of the isolated enzyme. It is deduced that lateral bud development is dependent on the synthesis of a cytokinin, which may take place by a biochemical route similar, but probably not identical, to that for adenine. It follows that this synthesis takes place locally in the bud itself.