The metabolism and biological activity of a 9-substituted cytokinin.

In order to test the metabolic stability of 9-substituted cytokinins, 6-benzylamino-9-methyl purine has been synthesized and labeled with (14)C in the 9-methyl carbon or doubly labeled with (14)C in the 9-methyl carbon and (3)H in the methylene moiety of the side chain. Although the 6-benzylamino-9-methylpurine is chemically stable, cytokinin-requiring tissues begin removing the 9-substituent in as little as 10 minutes. Among the various metabolic products is free benzylaminopurine. Thus, the biological activity of 9-substituted cytokinins could be accounted for by their conversion to the free base.