Water status and growth responses of wheat (T. aestivum L. [GWO-1809]) to increased CO2 concentration and water stress were studied in controlled-environment chambers. Plants were grown in 350 .mu.l/l or 1000 .mu.l/l CO2 at similar temperature, irradiance and photoperiod conditions. Groups of plants were subjected to water stress by withholding irrigation for 1 or 2 cycles of treatment. In most treatments, decreasing leaf water potential was correlated with decreasing osmotic potential. In leaves grown in both low and high CO2 concentrations, the osmotic potentials were lower during the 2nd stress cycle than during the 1st cycle. The stomata of plants in the low CO2 concentration closed at a higher leaf water potential than those in the high CO2 concentration. Stem and head production was greater in plants grown in high CO2 concentrations than those grown in low CO2, perhaps the result of turgor-pressure maintenance as leaf water potential decreased. In controlled-environment chambers, wheat plants adapted to water stress, apparently because of high CO2 concentration and repeated stress cycles.