Cytokinins and the regulation of plant form in three species of Sophora

Possible relationships between cytokinins and juvenile form of Sophora species were investigated. Exogenous applications of 6‐benzylaminopurine (6‐BAP) to seedling S. microphylla resulted in a more divaricating appearance. Treated plants had more outgrown branches, wider branch angles, and narrower node angles than control plants. 6‐BAP at 50 μmol/1 concentration was more effective in promoting this change than at a concentration of 150 μmol/1. The form of S. prostrata was not altered by exogenous application of cytokinin. Endogenous levels of storage and active cytokinins were assayed in pot‐grown material, using high performance liquid chromatography and radioimmunoassay. Compounds with retention times and antibody specificity typical of known cytokinins in other species, were detected in S. microphylla, S. prostrata, and S. tetraptera. The recovery rates were low (1.5‐18%) and results are difficult to interpret because of large amounts of an unknown cytokinin. However, it appears that the ratio of active to storage cytokinin is greater in the divaricating than non‐divaricating forms.