Temperature and long-day lighting strategy affect flowering time and crop characteristics in Cyclamen persicum

Abstract

Long-day treatments such as day extension (DE) and night interruption (NI) lighting during short day and cold seasons can promote the growth and flower development of Cyclamen persicum and cyclic NI lighting (CL) can reduce the lighting cost as compared with continuous NI. To compare the effect of CL with continuous NI or DE under different temperatures, cyclamen (Cyclamen persicum Mill.) ‘Metis Red’ was grown until full bloom at 12, 16, or 20°C during dark period in combination with six photoperiods: 9-hour short days (08:00–17:00) with natural sun light (SD), SD + 6-hour DE (17:00–23:00), SD + 2-hour (23:00–01:00) or 4-hour (22:00–02:00) NI, and 10% [6 min on and 54 min off (6/54) for 4-hour] or 20% [6 min on and 24 min off (6/24) for 4-hour] CL. Compact fluorescent lamps used as the light source delivered about 3 mol·m⁻²·s⁻¹ PPFD at the canopy level. Plants grown at 20°C during the dark period had visible buds and open flowers earlier by 7 days than those grown at 16 or 12°C. The NI and CL hastened flower bud initiation and flowering, and promoted plant growth as compared with SD at each growing temperature. Plants grown at 16 and 12°C with all NI treatments had the higher numbers of flower buds, leaves, and flowers than those grown at 20°C under SD. Using CL lighting and 16°C could reduce cyclamen production costs during winter by as much as 83% as compared to a natural light and 20°C. Therefore, CL can substitute for continuous NI or heating that enhances the flowering of cyclamen during SD and cold seasons, reducing heating and lighting costs.