- 著者
- Kazuhiro FUJIWARA Shunsuke KUBO Kensuke EIJIMA Ryo MATSUDA Akira YANO
- 出版者
- The Society of Agricultural Meteorology of Japan
- 雑誌
- 農業気象 (ISSN:00218588)
- 巻号頁・発行日
- vol.78, no.3, pp.101-112, 2022-07-10 (Released:2022-07-10)
- 参考文献数
- 26
We have improved a light-emitting diode artificial sunlight source system that we developed in 2013. The 2013 system can produce light with various spectral distributions for wavelengths of 380-940 nm that approximates those of ground-level sunlight and produce light with arbitrarily modified spectral distributions. Moreover, this system can produce time-varying light with different spectral distributions. However, this system’s utility is limited because the light it produces has low maximum irradiance and low time-stability for sunlight-effect research experiments. Hardware and software improvements to that system allow it to now produce a maximum irradiance of approximately 1.54 kW m-2 for 380-940 nm at a 7.1 cm2 light outlet with greater time stability and make it easier to produce time-varying light having a large number of different spectral distributions. First-step operational tests showed that this improved system can accurately produce single light with spectral irradiance distributions (SIDs) approximating: (1) SIDs of ground-level sunlight measured in Tokyo at two-hour intervals on a clear day; (2) various magnifications (1.33, 1.2, 1, 1/10, 1/100, and 1/1000 times) of a reference terrestrial solar SID, which is defined by the International Electrotechnical Commission; and (3) various geometric-shape SIDs as arbitrarily modified ones, except for a rectangular shape. For the second-step operational test, time-varying light with the three SIDs described above was produced in various sequences at three-second intervals. The third-step operational test verified the 30-min time stability of SID at the light outlet. Operational tests indicate that the improved system can facilitate various sunlight-effect research. Our improved system enables sunlight-effect research experiments that were previously impossible, such as investigations of naturally fluctuating sunlight effects on plant response, growth, and development. Moreover, experiments comparing the effects of ground-level sunlight spectral distribution and conventional artificial lamps on plant growth and development are now possible.
- 著者
- Tomohiro Jishi Kazuhiro Fujiwara Kyohei Nishino Akira Yano
- 出版者
- The Illuminating Engineering Institute of Japan
- 雑誌
- Journal of Light & Visual Environment (ISSN:03878805)
- 巻号頁・発行日
- vol.36, no.3, pp.88-93, 2012-12-01 (Released:2013-03-04)
- 参考文献数
- 9
- 被引用文献数
- 3 12
The CO2 uptake rate (CUR) of the aerial part of cos lettuce (Lactuca sativa) was measured in pulsed and continuous light at an average photosynthetic (wavelength range: 400–700 nm) photon flux density (PPFD) of 100 μmol m-2 s-1 from white light-emitting diodes (LEDs). Three duty ratios of 25, 50, and 75%, combined variously with eight frequencies of 0.1, 0.2, 0.4, 0.8, 1.6, 3.2, 6.4, and 12.8 kHz were used for pulsed light irradiation. The CURs were significantly lower at a duty ratio of 50% for frequencies of 0.1–0.8 kHz and at a duty ratio of 25% for all frequencies than those in continuous light although the average PPFD was unchanged. These results indicate that pulsed light at lower duty ratios, combined with lower frequencies, makes CUR of cos lettuce lower than that attained in continuous light. We infer, based on a PPFD-CUR curve obtained with cos lettuce plant used in the experiment, that when greater PPFD is provided, pulsed light at lower duty ratios with lower frequencies is less advantageous than continuous light for photosynthesis.