Plant growth under white LEDs compared with under fluorescent lamps.

摘要

In a plant factory, the selection of an appropriate light source is essential to create an artificial environment for cultivation. Since characteristics of light sources affect plant growth, it is desirable to investigate the effects of the different spectra and to develop more effective light sources. So far, we have seen that some leafy vegetables under some white light emitting diodes (LED) become larger than those under 3-band fluorescent lamps after 16 days of treatment. The experimental results would show that the white LED shows a greater red photon flux and less of a blue one. In this paper, tomato was grown under the fluorescent lamp and 3 types of white LEDs to compare these growths depending on the characteristics of light sources; R/B ratio, photosynthetic photon flux per electrical power supplied. Four equipments, which were composed of the white LEDs and three band fluorescent lamps, were set in a controlled environment. The respective height of these light sources was regulated to maintain an average horizontal photosynthetic photon flux density (PPFD) on cultivation beds in these equipments as possible to evaluate the effect of the spectrum of these light sources. The relative spectral radiant intensities of these light sources were measured by a multi-channel spectroradiometer at 5 nm intervals. R/B ratios of these light sources calculated from the relative spectral radiant intensities were from 0.68 to 1.67. There was little difference among these 4 types of light sources in 23 days after transplanting. The experimental results would show that PPFD distributions on the cultivation beds were nearly the same among the four light sources. Considering PPF/W ratio the LEDs were appropriate for cultivation, more than the fluorescent lamp.