Biosynthesis of cytokinins by tobacco cell cultures

In synchronously cultured tobacco cells (Nicotiana tabacum cv.Xanthi), the incorporation of U-¹⁴C-adenosine into butanol-solublecytokinins in vivo was studied. The radioactivity was incorporatedinto zeatin, ribosylzeatin, isopentenyladenosine and glucosylzeatinafter 20 min. The radioactive cytokinins were identified bythin-layer chromatography and high performance liquid chromatography.From the short time course of the incorporation of ¹⁴C-adenosineinto butanol-soluble cytokinins, the presence of the followingbiosynthetic pathway in vivo was suggested: adenosine is converedinto isopentenyladenosine and then into zeatin via ribosylzeatin.The biosynthetic pathway of free cytokinins in vivo is comparedwith that in vitro. (Received June 20, 1980; )