The mode of incorporation of 6-benzylaminopurine into tobacco callus transfer ribonucleic Acid: a double labeling determination.

Cytokinin-dependent tobacco (Nicotiana tabacum) tissue was grown in the presence of N(6)-benzyladenine (6-benzylaminopurine) labeled in the phenyl ring with (3)H and in the 8-position of the purine ring with (14)C. The (3)H/(14)C ratio of N(6)-benzyladenosine recovered from labeled tobacco callus transfer RNA preparations was compared with the corresponding ratio for N(6)-benzyladenine supplied in the medium. By this means, with suitable controls, the incorporation of the synthetic cytokinin, N(6)-benzyladenine, into the transfer RNA of tobacco callus tissue was shown to involve the intact moiety. The observed level of incorporation was up to one N(6)-benzyladenosine molecule per 10(4) transfer RNA molecules.