Isolation and Estimation of Cytokinins and Cytokinin-Containing Transfer RNAs from Cucumis

N6-({Delta}2-Isopentenyl) adenosine antibodies were used for the isolation of free cytokinins and cytokinin-containing tRNAs from parts of Cucumis sativus L. var. Guntur seedlings and for the estimation of cytokinins in them. Immobilized N6-({Delta}2-isopentenyl) adenosine antibodies retained tRNAs containing N6-({Delta}2-isopentenyl) adenosine and N6-(4-hydroxy-3-methylbut-2-enyl) adenosine with equal efficiencies. There were at least five cytokinins in the free form in cucumber seedlings. N6-(4-Hydroxy-3-methylbut-2-enyl) adenosine, N6-({Delta}2-isopentenyl) adenosine, and N6-({Delta}2-isopentenyl) adenine were present at least to the extent of 80, 23, and 9 nanograms, respectively, in the cotyledons and 40, 6, and 3 nanograms, respectively, in the decotyledonated seedlings per gram of tissue. Only two cytokinins were found in the tRNAs of cucumber cotyledons, namely N6-({Delta}2-isopentenyl) adenosine and N6-(4-hydroxy-3-methylbut-2-enyl) adenosine in amounts of 12 and 318 nanograms, respectively, per gram of tissue. Immunoaffinity chromatographic analysis of radiolabeled aminoacyl tRNAs from cucumber cotyledons showed that tRNAPhe and tRNATyr contained cytokinins whereas tRNAAla did not.