Effects of Opening and Closing of a Plastic Tunnel on Microclimate and Gas Exchange of a Grafted Tomato-Transplant Community during the Acclimatization Stage

Abstract

Net photosynthetic and evapotranspiration rates of a grafted tomato-transplant community and microclimate around the transplant community during acclimatization using a plastic tunnel in a greenhouse were measured using micrometeorological and weighing method. When the tunnel was opened, net photosynthetic and evapotranspiration rates of the transplant community increased linearly with air current speed around the transplant community. The air current speed decreased almost to near 0 m s^-1after closing the tunnel. When the tunnel was closed, net photosynthetic and evapotranspiration rates of the transplant community were -0.02 mgCO₂m^-2s^-1and 3 mgH₂O m^-2s^-1, respectively. They were similar to the rates when the air current speed was almost 0 m s^-1with the tunnel opened. Therefore, decreased photosynthetic and evapotranspiration rates when the tunnel was closed were considered to be the result of inhibition of gas exchange between transplants and atmosphere engendered by decreased air current speed.