Influence of Photoperiod and Growth Regulators on Flowering of Rhipsalidopsis gaertneri

Abstract

Abstract Plants of Rhipsalidopsis gaertneri [Regel] Moran ‘Crimson Giant’ were given continuous 14-hr long-days (LD), provided by 8-hr daylight plus 6-hr incandescent (Inc) irradiation; continuous 8-hr short-days (SD), provided by daylight; 2, 4, 6, or 8 weeks SD, then LD; or 2, 4, 6, 8 weeks LD, then SD. All plants receiving continuous LD or 2, 4, 6, or 8 weeks SD then LD flowered, whereas some or all plants in other photoperiod regimes failed to flower. Earliest and most prolific flowering occurred in response to 4, 6, or 8 weeks SD then LD. In a second experiment, plants previously given 8 weeks of 8-hr daylight (SD) were transferred to one of the following photoperiods: 12-, 14-, 16-, or 20-hr (8 hr daylight plus = to 12-hr Inc irradiation); 8-hr daylight plus 4-hr Inc night interruption (NI); or 8-hr daylight (SD). All plants receiving photoperiods of 12 to 20 hr or 4-hr NI flowered. Days from start of photoperiod treatments to visible flower buds was inversely related to duration of the Inc irradiation period, with a 4-hr NI comparable to 16-hr day. Days required for visible flower buds to complete development (flower expansion) were largely unaffected by duration or timing of Inc irradiation. Application of BA delayed flowering but more than doubled the number of flower buds per flowering apical phylloclade. Flower bud abortion was increased and both flower fresh weight and flower diameter were diminished by BA. Application of STS did not reduce flower bud abortion on BA-treated plants, but increased the percentage of apical phylloclades flowering. Chemical name used: N-(phenylmethyl)-lH-purin-6-amine (BA), silver thiosulfate (STS).