Temperature and photoperiodic regulation of flowering in 'Crimson Giant' Easter cactus.
1991
Boyle T.H.
Experiments were performed to determine the effects of photoperiod and temperature on flowering of the short-long-day plant (SLDP) Rhipsalidopsis gaertneri (Regel) Moran 'Crimson Giant'. At 18C night temperature (NT), photoperiods from 8 to 11 hours were equally effective in satisfying the short-day (SD) phase, whereas photoperiods greater than or equal to 12 hours were less effective but not completely inhibitory to flowering. Prolonging the exposure to either 10 or 18C NT under 9- to 10-hour natural daylengths (ND) delayed flowering but increased the percentage of apical phylloclades flowering, number of flower buds per flowering apical phylloclade, and number of flower buds per plant. Plants grown at 10C NT and ND for 6 to 8 weeks developed more flower buds and flowered at the same time as or earlier than plants subjected to 18C NT and ND for an equivalent span. Following 8 weeks at 10C NT, plants forced at 18C NT flowered earlier and the number of flower buds was higher when exposed to approximately 14-hour long days (LD) compared with 8-hour SD; number of flower buds was highest when plants received greater than or equal to 5 weeks of LD. Flowering did not occur under 18C NT and 8-hour SD unless plants previously received greater than or equal to 6 weeks at 10C NT. Thus, both temperature and photoperiod are critical for controlled flowering of 'Crimson Giant'.
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