Field measurements of photosynthesis, water-use efficiency, and growth inAgropyron smithii (C) andBouteloua gracilis (C) in the Colorado shortgrass steppe.

Field measurements of gas exchange and growth were conducted on a C grass,Agropyron smithii, and a C grass,Bouteloua gracilis, in order to further establish the adaptive significance of the C pathway under natural conditions. Maximum rates of leaf area expansion in tillers and maximum seasonal photosynthesis rates of both species occurred during the cool, early summer month of June. The occurrence of maximum growth and photosynthesis inB.