Effects of far-red light irradiation and its timing on the flowering in Phalaenopsis amabilis

In this study, we investigated the effect of far-red (FR) light irradiation on the flowering of Phalaenopsis. For the experimental material, Phalaenopsis amabilis, which is one of the important breeding parents of the current commercial cultivars and is also used for commercial cultivation, was selected. Firstly, they were cultivated in a closed environment for over 4 years using blue (B), green (G), red (R), and FR light emitting diodes (LEDs). A comparison of the over 4-year cumulative flowering reactions showed that the flowering was most promoted under the R light and least inferior under the G light. Surprisingly, although the FR light is not effective for photosynthesis, the flowering reaction under FR light like to that under the B light was observed, and it was expected that the flowering promotion effect of the FR light was different from that of the R light. Secondary, we investigated the effects of FR LED supplemental lighting under common greenhouse cultivation. When the effect was verified by supplementing the greenhouse-grown plants with FR LED light, the supplemental lighting for 4 h at midnight was ineffective, but the end of day (EOD) irradiation for 4 h clearly promoted flowering. This result is considered to lead to a new flowering promotion technology of Phalaenopsis.