Mode of action of N,N'-diphenylurea: The isolation and identification of the cytokinins in the transfer RNA from tobacco callus grown in the presence of N,N'-diphenylurea.

The tRNA from cytokinin-dependent tobacco callus (Nicotiana tabacum) grown on mineral medium containing N,N'-diphenylurea as the source of cytokinin was found to contain 3 cytokinin-active ribonucleosides. The 2 ribonucleosides present in the largest amounts were identified conclusively by their chromatographic properties, ultra-violet and low-resolution mass spectra as the naturally-occurring cytokinins 6-(4-hydroxy-3-methyl-cis-2-butenylamino)-9-β-D-ribofuranosylpurine and 6-(3-methyl-2-butenylamino)-9-β-ribofuranosylpurine. A third ribonucleoside, present in smaller amounts, was identified as another naturally-occurring cytokinin 6-(4-hydroxy-3-methyl-2-butenylamino)-2-methylthio-9-β-D-ribofuranosylpurine on the basis of its chromatographic behaviour. No evidence was found to associate the mode of action of the non-purine cytokinin, N,N'-diphenylurea, with tRNA.