Biosynthesis of Cytokinins in Cytokinin-Autotrophic Tobacco Callus

A cytokinin-autotrophic strain of tobacco callus contained cytokinin-active compounds with chromatographic mobilities on Sephadex LH-20 corresponding to ribosylzeatin, zeatin, and 6-Δ2 -isopentenylaminopurine. Zeatin, the apparent major cytokinin, was estimated to be present at a concentration of 10-4 μmol/kg of tissue. Cytokinin-autotrophic callus supplied with [14 C]adenine produced radioactive components with the same chromatographic properties as zeatin and 6-Δ2 -isopentenylaminopurine. These components were not obtained from cytokinin-dependent tissue supplied with [14 C]adenine in the same manner.