ABSTRACT
The cytokinin-autotrophic tobacco pith tissue culture used by C. M. Chen and D. K. Melitz and Chen was originally isolated by J. E. Fox and has been grown on a culture medium devoid of cytokinin and auxin. An understanding of the biosynthetic path way of cytokinins would provide basic knowledge for regulating the hormone in plant cell division and differentiation. Paper electrophoretic analysis of the extracted products, with unlabeled markers, will tentatively identify the biosynthesized radioactive cytokinins. The amount of radioactive i6Ado can be determined by liquid scintillation counting. The reaction product extracted with water-saturated ethylacetate is reduced to a small volume, fractionated over a column of Sephadex LH-20, and further characterized by paper chromatography, in various solvent systems, and/or by high-performance liquid chromatography. The final step of purification, DEAE-cellulose column chromatography, resulted in a specific activity of 10,700 units per milligram of protein.
