2017 年 29 巻 3 号 p. 73-80
To achieve higher production in greenhouses, maximization of crop net photosynthesis is required; hence, CO2 enrichment and supplemental lighting equipment has been installed in many commercial greenhouses. In practice, appropriate profitability analysis should be performed before such installations. Crop growth and yield simulation models based on the environmental response of leaf photosynthesis are useful to evaluate the increase in profitability derived from the new equipment. Therefore, accurate and compatible data on the environmental response of leaf photosynthesis are necessary. In this study, we proposed a general protocol for the measurement of leaf photosynthesis environmental response, i.e., light response curve and CO2 response curve, that can be widely applied to the crops grown in greenhouses. Furthermore, the effects of stomatal opening/closure and phosphate limitation on the photosynthesis of tomato leaves through the proposed measurement protocol were investigated. The results demonstrated that the effects of stomatal opening/closure on the photosynthetic rate during light response curve measurement are small, particularly under high CO2 concentrations; however, the stomata tended to be closed when the measurement was performed on a cloudy day. Moreover, in the measurement of CO2 response curve, the stomatal response to CO2 concentration differs depending on PPFDs, i.e., stomata tended to close under high CO2 concentrations (> 400 μmol mol-1) at a PPFD of 500 μmol m-2s-1, but not at PPFDs of 1000 and 1500 μmol m-2s-1. Furthermore, a slight but significant decrease in photosynthetic rate, which might be caused by phosphate limitation, was observed at high PPFD and high CO2 concentration.