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 N⁶-benzyladenine (6-benzylaminopurine) labeled in the phenyl ring with ³H and in the 8-position of the purine ring with ¹⁴C. The ³H/¹⁴C ratio of N⁶-benzyladenosine recovered from labeled tobacco callus transfer RNA preparations was compared with the corresponding ratio for N⁶-benzyladenine supplied in the medium. By this means, with suitable controls, the incorporation of the synthetic cytokinin, N⁶-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 N⁶-benzyladenosine molecule per 10⁴ transfer RNA molecules.