Biosynthesis of cytokinins by tobacco cell cultures

Abstract
In synchronously cultured tobacco cells (Nicotiana tabacum cv. Xanthi), the incorporation of U-14C-adenosine into butanol-soluble cytokinins in vivo was studied. The radioactivity was incorporated into zeatin, ribosylzeatin, isopentenyladenosine and glucosylzeatin after 20 min. The radioactive cytokinins were identified by thin-layer chromatography and high performance liquid chromatography. From the short time course of the incorporation of 14C-adenosine into butanol-soluble cytokinins, the presence of the following biosynthetic pathway in vivo was suggested: adenosine is convered into isopentenyladenosine and then into zeatin via ribosylzeatin. The biosynthetic pathway of free cytokinins in vivo is compared with that in vitro.