The Continuous Measurement of Photosynthesis, Respiration, and Transpiration of Alfalfa and Wheat Growing Under Field Conditions

The apparatus and experimental technique which are described in this paper have been developed to determine continuously, automatically, and throughout the life of a plant, if desired, the carbon dioxide exchange and the transpiration in a chamber in which plants are growing under field conditions. This discussion gives a general resume of our methods, including, first, a description of the equipment ; second, illustrations of its application to alfalfa and wheat ; third, a statistical analysis of the data, showing the magnitude of the errors and variability involved ; and fourth, some interesting observations on the relation of light intensity and temperature to the rate of photosynthesis, respiration, and transpiration, which these methods have made clear.