Carbon dioxide exchange in water - stressed sorghum

Moench) in a growth chamber as it dried out from a freshly watered condition to severe water stress. Carbon dioxide uptake in the light decreased to near the compensation point at water potentials near -25 atmospheres. Leaf resistance to gaseous exchange was high at this point. Evolution of CO2 in the light occurred as stress became greater. Dark evolution of CO2 was higher at water potentials near -20 atmospheres than in either the more severely stressed or non-stressed condition. The activity of phosphoenolpy ruvic carboxylase remained comparatively high as water stress increased.