Transpiration and Stomatal Opening with Changes in Carbon Dioxide Content of the Air.

Increasing the carbon dioxide content of air reduces the transpiration rate of corn and sorghum plants and, to a lesser extent, of cotton, soybean, and tomato plants by causing the stomata to close. Closure of corn and sorghum stomata occurred when the concentrations of carbon dioxide were 2000 and 3000 parts per million, respectively. Cotton, soybean, and tomato stomata did not close completely at concentrations of carbon dioxide up to 4000 parts per million.