Photoperiod, Irradiance, and/or Cool Temperature Effects on Lobivia × Chamaecereus Hybrid `Rose Quartz' Flowering

Abstract

Photoperiod, irradiance, and/or a cool temperature effects on Chamaelobivia hybrid `Rose Quartz' flowering was studied. Two- to 3-year-old plants were grown for 4 months under natural daylight (DL; August–November) in a greenhouse maintained at 26 ± 2 °C. Plants were then placed in either of two greenhouses: a cool temperature house (5 ± 2 °C; natural daylight), or a lighting treatment house (22 °C day/18 ± 1 °C night temperature, respectively). The lighting treatment house had eight light environments: 1) short day (SD; 8 h; 0800–1600 HR); 2) SD+25–35 μmol·m-2·s-1; 3) SD+45-50 μmol·m-2·s-1; 4) SD+85-95 μmol·m-2·s-1; 5) DL plus night interruption lighting (NI; 2200–0200 HR; 2 μmol·m-2·s-1 from incandescent lamps); 6) DL+25-35 μmol·m-2·s-1 (lighted from 0800–0200 HR); 7) DL+45-50 μmol·m-2·s-1; and 8) DL+85-95 μmol·m-2·s-1. Supplemental lighting was provided using high-pressure sodium lamps. Plants were placed in the cool temperature environment for 0, 4, 8, or 12 weeks before being placed under lighting treatments. All plants received a 6-week lighting treatment and were then placed in the finishing greenhouse (22 ± 2 °C). Data were collected on the date when each flower opened (five only), the flower number per plant, and flower longevity (five only). Vernalization interacted with photoperiod to affect flowering. Unvernalized plants exhibited an obligate long-day requirement for flowering. Vernalized plants exhibited a facultative long-day requirement for flowering. The impact of vernalization, photoperiod, and irradiance on flower number, time to flower, and longevity will also be discussed.