Night Interruption and Cyclic Lighting Using LEDs Promote Flowering and Save the Production Cost of Cyclamen In Winter

Night interruption (NI) and cyclic lighting (CL) are used as an alternative method to heating for promoting cyclamen flowering. This study was conducted to investigate the effect light quality during NI and CL on flowering. Two species of cyclamen [Cyclamen persicum ‘Scarlet Red’(SR) and ‘Scarlet Purple’(SP)] were grown under four different light sources (fluorescent, red LED, far-red LED, blue LED) with combination of NI (4 h) and CL (6’/24’ on/off for 4 h) around midnight in a growth chamber. Short-day (SD) was 9 h. Photosynthetic photon flux was 300 µmol·m^-2·s^-1 with three-wave fluorescent lamp during day time and 3-15 µmol·m^-2·s^-1 with fluorescent lamp and LEDs of each wave for NI and CL, respectively. Temperature was optimum for cyclamen growth (24/16^oC, day/night). NI and CL treatment hastened flowering in both Cyclamen persicum SR and SP. Cyclamen persicum SR and SP reached flowering maximum 19 and 12 days, respectively, earlier than plant grown at SD condition. There was no significant difference in flowering time of both SR and SP among light sources at each NI and CL. There was no significant difference in the number of visible buds and flowers among light treatments and light sources. However, plant length and width tended to increase at both NI and CL with far-red LED than those at other LEDs in both SR and SP. The number of visible buds significantly decreased at CL with blue LED in SP. In addition, the number of flowers at NI with blue LED was less than those at NI with red LED. Although, there were some differences between SR and SP, plant grown under NI and CL with far-red and blue LED produced poor quality commodities of Cyclamen persicum than those under NI and CL with red LED. Electricity consumption of LED was about 60 percent of fluorescent lamp. Fluorescent lamp was widely used at NI and CL treatment in general. These result indicated that red LED could replace the fluorescent lamp for promoting cyclamen flowering at NI and CL due to electricity cost. For details in cost saving, more economical analysis is necessary including both investment and operating cost of LED lamps in a commercial greenhouse.

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