Photoperiod, chilling, and light quality during daylight extension affect growth and flowering of tissue-cultured Easter lily plants

Easter lily plants (Lilium longiflorum Thunb.), derived from tissue culture and grown continuously, were subjected to various photoperiod and chilling treatments. Lilies grown with daylength extended either with high-intensity discharge (HID) or incandescent lights flowered in the same number of days, but had more flower buds with HID lamps. Flowering was delayed and plants produced more leaves as photoperiod was reduced from 16 to 12 hours. The numbers of leaves, primary, secondary, and tertiary flowers, and the time to flower were all significantly reduced as the duration of extended lighting was increased from 0 to 6 weeks. As the number of weeks of cooling at 5°C increased from 0 to 5, time to flower was significantly reduced.