Effects of air current on transpiration and net photosynthetic rates of plants in a closed plant production system

摘要

The effects of the air current speed less than 1 m s~(-1) on transpiration (Tr) and net photosynthetic rates (Pn) of sweetpotato leaves and on a canopy of rice plants were determined using a chamber method and a combination of micro-meteorological and weighing methods, respectively. The effects of vertically downward moving and horizontal air currents on the Tr were also compared using a model plant canopy made from wet papers. The Tr and Pn of sweetpotato leaves were doubled as the air current speed increased from 0.01 to 0.3 m s~(-1) and was almost constant at air current speeds 0.3-1.0 m s~(-1). The Tr and Pn of the rice plant canopy increased linearly by 2.5 and 2 times, respectively, as the horizontal air current speed increased from 0.01 to 0.8 m s~(-1). Horizontal air current speeds above 1 m s~(-1) are necessary to obtain maximal Tr and Pn of the canopy. The Tr of the model plant canopy was 2-3 times greater with the vertically downward air current than in the horizontal air current in an air current speed of 0.15-0.3 m s~(-1). A vertically downward air current at 0.3 m s~(-1) around leaves would be adequate for promoting Tr and Pn and thus plant growth in a closed plant production system.