01868nas a2200181   4500008004100000245014500041210006900186300001300255490000800268520125600276653002001532100002101552700002101573700002001594700001401614700001801628856004001646       1997                        eng d00aPhotosynthetic gas exchange and water relations responses of three tallgrass prairie species to elevated carbon dioxide and moderate drought0 aPhotosynthetic gas exchange and water relations responses of thr  a608 -6160 v1583 aUndisturbed tallgrass prairie was exposed to ambient and elevated (twice-ambient) levels of atmospheric CO2 and experimental dry periods. Seasonal and diurnal midday leaf water potential (Ψ leaf), net photosynthesis $(A_{\text{net}})$, and stomatal conductance (g s) responses of three tallgrass prairie growth forms—a C4 grass, Andropogon gerardii; a broad-leaved woody C3 shrub, Symphiocarpos orbiculatus; and a C3 perennial forb, Salvia pitcheri—were assessed. $\Psi _{\text{leaf}}$ in A. gerardii and S. orbiculatus was higher under elevated CO2, regardless of soil moisture, while $\Psi _{\text{leaf}}$ in S. pitcheri responded only to drought. Elevated CO2 always stimulated $A_{\text{net}}$ in the C3 species, while A. gerardii $A_{\text{net}}$ increased only under dry conditions. However, $A_{\text{net}}$ under elevated CO2 in the C3 species declined with drought but not in the C4 grass. Under wet conditions, g s reduced in elevated CO2 for all species. During dry periods, gs at elevated CO2 was sometimes higher than in ambient CO2. Our results support claims that elevated CO2 will stimulate tallgrass prairie productivity during dry periods and possibly reduce temporal and spatial variability in productivity in these grasslands.10aWater relations1 aHamerlynck, E.P.1 aMcAllister, C.A.1 aKnapp, Alan, K.1 aHam, J.M.1 aOwensby, C.E.  uhttp://www.jstor.org/stable/2474921