Hormones in Plants Bearing Nitrogen-fixing Root Nodules: Cytokinin Transport from the Root Nodules of Alnus glutinosa (L.) Gaertn.

The movement and metabolism of [8-¹⁴C]zeatin applied to theroot nodules of Alnus glutinosa (L.) Gaertn, was investigated.Twenty-four hours after the start of uptake, zeatin and a numberof its metabolites were detected in all parts of the plant.The major radioactive compounds present in a cationic fractionof different plant parts at this time co-chromatographed onSephadex LH20 with zeatin (in nodules, stems, and leaves) andwith zeatin riboside (in roots, stems, and buds). In the roots,in addition to the peak co-chromatographing with zeatin riboside,there was also a prominent unidentified polar peak. The presence of zeatin and zeatin riboside in the stems andleaves was indicated also by chromatographic behaviour in othersystems, effects of permanganate oxidation, and cocrystallisationwith the authentic unlabelled compounds. Biological activitywas exhibited by both peaks in the soybean callus bioassay.Other metabolites in the shoot, possibly active as cytokinins,had the characteristics of dihydrozeatin, zeatin or dihydrozeatin-5'-nucleotide(s),and zeatin or dihydrozeatin glucosides. The gradual disappearancewith time of zeatin and its riboside from the shoot was accompaniedby an increase in the proportion of more polar metabolites. These results are discussed in relation to the possible exportof endogenous cytokinins by the nodules.