CO2 and air circulation effects on photosynthesis and transpiration of tomato seedlings

In the daytime, a CO2 depletion of 10-15% and air circulation of less than 05 m s(-1) often occur in a naturally ventilated greenhouse during a sunny day with high wind speed (3-5 m s(-1)) We, therefore, investigated the effects of moderate increase of the CO2 concentration above the atmospheric level (500-600 mu mol mol(-1)) and air circulation up to 1 0 ms(-1) in a growth chamber on the net photosynthetic and transpiration rates of tomato seedlings as the first step. The average net photosynthetic rates were 2.1, 1 8, and 1.6 times higher in the growth chambers with increased CO2 concentration (500-600 mu mol mol(-1)) and air circulation (1.0 ms(-1)). Increased CO2 concentration, and increased air circulation, respectively, compared with those in the control (no increase in CO2 concentration (200-300 mu mol mol(-1)) or air circulation (0.3 m s(-1)) The transpiration rate increased with increased air circulation, while it decreased with increased CO2 concentration regardless of air circulation From the results, we consider that increasing the CO2 concentration and/or air circulation in ventilated greenhouses up to the outside concentration (350-450 mu mol mol(-1)) and 10 ms(-1), respectively, can significantly increase the net photosynthetic rate of greenhouse plants Crown Copyright (C) 2010 Published by Elsevier B V All rights reserved