Control of Greenhouse Humidity and Airflow with Fogging and Circulation Systems and Its Effect on Leaf Conductance in Cucumber Plants

Fogging and circulation systems were installed into a greenhouse to control daytime humidity and airflow at adequately high levels, with systems composed of 9 mist sprayers and 2 fans with a diameter of 0.3 m. The performance of the systems was examined by analyzing humidity (vapor pressure, relative humidity), wind speed, and leaf conductance (total conductance of stomata and leaf boundary layer) of cucumber plants under 2 conditions: with mist and fan treatment and with no treatment. Use of the systems brought increases in relative humidity from 22% to 76% and wind speed from 0.16 to 1.08 m s−1 at the center of the greenhouse, and further increased effects were also found over the cultivation area. Moreover, such increases in humidity and wind speed accelerated the leaf conductance by approximately 1.5 times. The results suggest that fogging and circulation systems could improve the greenhouse environment and leaf gas exchange during daytime.