2020 年 76 巻 2 号 p. 104-110
We investigated the combined influence of cooling using electric heat pumps and CO2 enrichment in a closed greenhouse equipped with a near infrared solar radiation (NIR)-reflecting film on the yield and quality of tomato fruits during the summer season. The air temperature of the ‘Control’ greenhouse were controlled through conventional natural ventilation windows, shading curtains and a fog cooling system. The air temperature of the ‘Closed’ greenhouse were controlled by cooling of electric heat pumps and a NIR-reflecting film curtain. The CO2 concentration was maintained at around 1000 μmol mol-1 in the Closed greenhouse. During the experiment period when the outside temperature of the greenhouses was relatively high, the mean daytime air temperature was cooler by more than 3 °C in the Closed greenhouse than that in the Control. The total dry weight of the tomato plants and fruit yield per plant at the end of the experiment was significantly higher in the Closed greenhouse compared to the Control. The result indicated that the improved yield and quality of the Closed greenhouse resulted from the air temperature being controlled within the optimal range for growth and the subsequent increased rates of fruit maturation and photosynthesis due to CO2 enrichment.
