VEGETABLE GROWTH AS AFFECTED BY ON-OFF LIGHT INTENSITY DEVELOPED FOR VEGETABLE FACTORY
The pulsed light illumination has two characteristics. One is the effect on the photosynthesis in short-term plant growth caused by sharp pulse generated at high frequency, another is the effect on photosynthesis in long-term plant growth caused by on-off light illumination based on duty ratio. From the agricultural point of view, the latter may be expected for saving electric energy in the plant factory.
In this study, effects of the on-off light illumination on the photosynthesis of plant are discussed in the biological aspect of energy saving.
The results show that photosynthesis increases corresponding to the increase of duty ratio in 500ppm, 950ppm CO2 concentration, but does not in low CO2 concentration such as 200ppm. No remarkable differences of photosynthesis are found between in the on-off light and continuous light when the quantum flux density is equal to each other. But photosynthesis increases as CO2 concentration becomes high in 230-μE·m-2·s-1 quantum flux density of of 100% duty ratio. In the on-off light of 50% duty ratio, photosynthesis can be kept in the level near to that in 350ppm CO2 concentration and 100% duty ratio if CO2 concentration is increased. So electric power could be saved without reduction of yield by regulating the duty ratio and CO2 concentration properly.