Water Use Efficiency in Plant Growth and Ambient Carbon Dioxide Level

This report examines the validity and explores the practical implications of the proposition that CO2 enrichment of the leaf environment enhances plant growth and, simultaneously decreases plant water use. A theoretical analysis of the water and carbon dioxide balance of plant leaves was made in the form of a computer program based upon known physiological facts. It predicts significant increases in water use efficiency by plants as CO is enriched, the size of the increase depending upon the external conditions. Experimental tests were conducted in an environmental simulator with stands of soybean, pepper and southern pea plants. The predictions of the model were substantially verified, with CO2 concentrations ranging from normal to six-fold normal. Although CO2 is obviously an ideal antitranspirant, the efficacy of its release in open stands is doubtful in view of plausible economic factors. Butt in enclosures this would be a different matter, and for such situations the present report gives a scientific basis for engineering and system analysis