Abstract
The elevated Γ-values of maize leaves under water strain have been found to be due to a reduction in the rate of carbon-dioxide intake during photosynthesis; these Γ-values do not respond to changes in the concentration of oxygen. No evidence has been found of an increased rate of carbon-dioxide evolution from illuminated maize leaves under water strain (photo-respiration) although the presence of glycollate in these leaves could be demonstrated.