Control of Ranunculus asiaticus Flowering by Photoperiod and Temperature

Abstract

Three-month-old plants of Ranunculus asiaticus L. `Bloomingdale Mix' were transplanted into 10-cm pots and placed in growth chambers at 12, 16, or 20°C and 8, 12, or 16 hours day length. The irradiance was 12 mol·d–1·m–2. The fastest appearance of flower buds and flowering occurred for plants grown at 16 hours day length and 16°C or 12 hours day length and 20°C. At 16°C, plants grown at 8 hours photoperiod required 7–10 more days to reach the stage of visible flower bud than those plants grown at 12 or 16 hours day length. The number of days to flower from the initiation of experimental conditions varied from 53 ± 3.7 days (168 days from seeding) for plants at 16-hour days and 16°C or 12-hour days and 20°C to 74 ± 2.7 days (189 days from seeding) for plants at 8-hour days and 16°C or 12-hour days and 12°C. Largest number of buds and flowers (15 ± 2.2 flower buds) was observed on plants grown at 12 or 16°C and 12-hour photoperiod. Conditions with 8- or 16-hour days at 16°C or 12-hour days at 20°C resulted in a smaller number of buds and flowers (9 ± 3.2 flower buds).