Effects of light quality during cultivation on the flowering and floret arrangement in Phalaenopsis amabilis

The main purpose of this experiment is to investigate the good shape of flowering potted plants of Phalaenopsis placing under the different light qualities for the commercial point of view in Japan. An ornamental plant Phalaenopsis amabilis (L.) Blume was used as the experimental material. Each plant was kept into different light chambers, which were irradiated with blue, green, yellow, red, and far-red LEDs having the peak wavelength of 470, 525, 590, 660 and 730 nm respectively. The temperature of light treatment chamber maintained at 23±2°C and lighting time was set to 16 h from 8:00 to 24:00, adjusting 80 µmol m^‑2 s^‑1 PPFD at the top of the plant samples. Flower stems were formed in all treatment plots and flowered. However, the flowering plant shape greatly varied depending on the light quality of the irradiation light. Under the blue or green light, the stem rose almost vertically, but in the yellow, red, especially in the far-red light, the stem drooped sideways. The angles between floret pedicel and flower stem axis under the blue and green light condition were narrow, and then all the florets were placed facing the front when viewing the flower stem from the front. On the other hand, the angles under yellow, red and far-red light were wide, and the florets on both sides of flower stem were arranged in a backward direction. According to the public choice in Japan, we think that the flower of the plant under the blue LED select as the good shape rather than the other light quality.