Identification of Photosynthesis of Crops as Affected by on-off Light Intensity

Abstract Recently, for saving electric power, an on-off driving fluorescent lamp has been developed for plant factory. As the on-off driving lamp is operated based on high frequency such as 37 kHz, it is very difficult for us to identify and estimate the effects on the photosynthesis of vegetable crops cultivated in such the artificial environment called as plant factory In this paper, we discussed the effects of the on-off light on the photosynthesis of vegetable crops with system identification method. We estimated the impulse responses in different CO2 concentration with spectral analysis by taking both the on-off light in different duty ratio and the response of photosynthesis as stationary stochastic processes. Simulation with the identified models showed a good agreement with the observed values. kesult showed us that the photosynthesis of the vegetable crops could be kept in a desirable level when the on-off light is regulated in low duty ratio if the CO2 concentration of the environment is increased. This indicates that electric power can be saved in the cultivation of vegetable factory if the on-off light illumination and the CO2concentration is controlled properly