Phytohormones, Rhizobium Mutants, and Nodulation in Legumes

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Abstract
[3H]Zeatin riboside was supplied to intact pea 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 3H 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 3H than the parent root. In both types of studies, metabolites with an intact zeatin moiety were detected in root nodules. In all experiments, 2-dimensional TLC revealed that little 3H remained as zeatin riboside in root or nodule tissue at the end of the labeling period. Nodules metabolized [3H]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 [3H]zeatin riboside. Furthermore, any differences between effective and ineffective nodules were generally minor.