2013 Volume 97 Issue 5 Pages 263-268
“Light pollution” due to outdoor lighting results in delayed heading time and reduced yield in rice. The purpose of this study is to assess the effect of light pollution by using a method whereby rice grows in a climate chamber and white LEDs (light emitting diodes) were used to simulate as outdoor lighting. We estimated heading time by quantitative determination of floral activator Hd3a in rice when five LEDs irradiated Oryza sativa L. cv Koshihikari in a dark period. As a result, three commercially supplied lights (light sources 1-3) and a customized light (light source 5) noticeably suppressed Hd3a expression and the estimated heading was delayed more than four days, indicating the occurrence of light pollution under 5lx irradiation. However, another customized light (light source 4) did not suppress Hd3a expression and estimated heading delay was within three days, indicating a reduction in light pollution. This stemmed from the difference in photon flux density with which each light source irradiated the rice. This suggests that illumination, in which light pollution is reduced (light source 4), of illuminance up to 10 lx does not suppress Hd3a expression, whereas over 15 lx does suppress Hd3a expression.
