Development of water treatment methods and crop management methods for suppressing crop photoinhibition

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The objective of this project was to develop an irrigation water treatment methods and/or crop management methods which could reduce photoinhibition of crop photosynthesis. Shirahata et al. (1997) reported that electrolyzed-reduced water had a power to scavenge active oxygen. Based on this report and an established knowledge that photoinhibition was caused by active oxygen, we made a working hypothesis : photoinhibition of crops could be reduced by giving them electrolyzed-reduced water. To verify this working hypothesis, we applied electrolyzed-reduced water to protoplasts from sweetpotato and determined the degree of photoinhibition by chlorophyll fluorescence (Mini-PAM) and also measured production rate of O2^- by luminescence from lucigenin. The results obtained did not support the working hypothesis. A measurement of O2^- scavenging power of electrolyzed-reduced water by Cytochrome C method did not support the hypothesis, either. Measurement of O^2- by ESR resulted in higher O2^- content in electrolyzed-reduced water compared to pure water.High cartenoid content in leaves is known to have a high ability of suppressing active oxygen production. Therefore, we investigated the possibility of reducing photoinhibition by controlling light quality (spectrum) applied to crops. We compared cartenoid contents in leaves of Komatsuna (Brassica campestris L) grown under blue, red and white fluorescence lamps. The results indicate that red light increased cartenoid content, compared to the other lights.