A SELECTIVE AUXIN AND CYTOKININ BIOASSAY BASED ON ROOT AND SHOOT FORMATION IN-VITRO

A new bioassay for auxins and cytokinins was developed based on de novo organogenesis. Auxin-dependent adventitious roots and cytokinin-dependent adventitious shoots were induced selectively in tobacco leaf disc culture incubated on nutritive-medium for 28 days. All auxins applied alone (indole, naphthalene, and phenoxyacetic acids) initiated roots, and all cytokinins used alone (purine and urea derivatives) initiated shoots at a concentration range of about 10(-9) M-10(-4) M. The bioassay separated the effects of auxins and cytokinins eliminating their synergistic effects. Abscisic acid and gibberellin (GA(3)) had no morphogenic activity.**