Phytohormones, Rhizobium Mutants, and Nodulation in Legumes

[(3)H]Zeatin riboside was supplied to intact pea (Pisum sativum) plants either onto the leaves or onto the root nodules. When applied directly to nodules, approximately 70% of recovered radioactivity remained in the nodules, approximately 15% was detected in the root system, and 15% was in the shoot. However, when supplied to the leaves, little (3)H was transported, with approximately 0.05% of recovered radioactivity being found in the root system and nodules. On a fresh weight basis, nodules accumulated more (3)H than the parent root. In both types of studies, metabolites with an intact zeatin moiety were detected in root nodules.In all experiments, two-dimensional thin layer chromatography revealed that little (3)H remained as zeatin riboside in root or nodule tissue at the end of the labeling period. Nodules metabolized [(3)H]zeatin riboside to the following cytokinins/cytokinin metabolites: zeatin, adenosine, adenine, the O-glucosides of zeatin and zeatin riboside, lupinic acid, nucleotides of adenine and zeatin, and the dihydro derivatives of many of these compounds.Although a few small differences were observed, there were no major differences between root and nodule tissue in their metabolism of [(3)H] zeatin riboside. Furthermore, any differences between effective and ineffective nodules were generally minor.