In agriculture, particularly wet rice cultivation, light pollution caused by exterior illumination at night interferes with dark periods and results in delayed flowering (heading). In this study, using light emitting diodes (LEDs), which make it relatively easy to irradiate selective wavelengths and control luminescence, the effects on the heading of rice of the wavelength of the light source it was exposed to at night and the control of luminescence (pulse emission frequency and duty ratio) were investigated through the expression of floral activator Hd3a. The results indicated that, under illumination with blue or green LEDs, the effect on the delay of flowering was small, but under illumination with near ultraviolet, yellow or red LEDs, it was large. Under illumination with yellow-green LEDs, it was predicted that heading would be delayed when the duty ratio was 100 ; however, when the duty ratio was 70 and the pulse emission frequency was 700 Hz, the effect on the delay of heading was small. Therefore, it was suggested that by selecting the wavelength of light sources that rice is exposed to and controlling luminescence, it is possible to bring the time of heading closer to that of total darkness (control plot).
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