STIMULATION OF BUD AND ROOT INITIATION IN LEAF CUTTINGS OF BEGONIA MASONIANA IRMSCH 'IRON CROSS' WITH GROWTH REGULATORS

Leaves of Begonia x masoniana Irmsch 'Iron Cross' collected bi-weekly were used to determine the levels of endogenous auxin and cytokinins for a 12-month period. The amounts of free IAA were increased under long days while bound IAA quantities were greatest during the period of short days. Six cytokinin-like substances similar to adenine, adenosine, zeatin, zeatin riboside, isopentenyl-adenine and isopentenyl-adenosine were detected in the begonia leaves. The amount varied with the season of the year with a profound increase observed under short day conditions. These changes in levels of endogenous auxin and cytokinin were found to be associated with changes in the regeneration ability of leaf cuttings.; The effects of exogenous applications of naphthalene acetic acid (NAA) 6-benzylamino purine (BA) and abscisic acid (ABA) on the regeneration ability of begonia leaf cuttings were determined. Three methods of application were compared including a quick dip (6-second), talc carrier dip and foliar spray with different concentrations for each method. The cuttings were propagated at one of four temperatures with two day lengths (short and long).; High concentrations of BA were found to stimulate bud formation and inhibit root formation whereas high concentrations of NAA had the opposite effects. However low concentrations of NAA promoted bud formation and low concentrations of BA had a stimulating effect on root formation.; Both BA and NAA enhanced bud and shoot regeneration. NAA stimulated bud and shoot development when applied to the cuttings at 1.2 (mu)M as a quick dip or 3 (mu)M talc carrier. Cuttings treated with 4.0 (mu)M BA quick dip or 6 (mu)M talc carrier successfully generated new plants. With certain BA and NAA combinations both shoots and roots were increased. The optimal combinations for plant production ranged 1.2-13.8 (mu)M NAA and 6.7-27 (mu)M BA. The number of shoots per cuttings were significantly increased when treated with 12 or 15 (mu)M NAA and four weeks later received spray applications of BA at 40 (mu)M. ABA at 0.02 - 0.4 (mu)M clearly enhanced bud and shoot formation in the presence of the optimal NAA concentration of 0.12 - 1.2 (mu)M. The quick dip was the best method tested. (Abstract shortened with permission of author.)...