Abstract: In three consecutive years (1983, 1984, and 1985) soybeans (Glycine max L. Merr. cv Bragg) were grown from seed to maturity in six outdoor environmentally controlled plant growth chambers under natural solar irradiance. The C0 2 concentrations inside the chambers were controlled to various levels during these studies. Both field and laboratory measurements were made to investigate the effects of CO2 concentration on photosynthesis...