Reference
Hakala, K. Helio, R., Tuhkanen, E. and Kaukoranta, T. 1999. Photosynthesis and Rubisco kinetics in spring wheat and meadow fescue under conditions of simulated climate change with elevated CO2 and increased temperatures. Agricultural and Food Science in Finland 8: 441-457.
What was done
The authors grew spring wheat (Triticum aestivum L. cv. Polkka) and meadow fescue (Festuca pratensis Hudson cv. Kalevi) in the field at Jokioinen in the southern part of Finland over the period 1992-1994. Plants were exposed to ambient and elevated (700 ppm) atmospheric CO2 concentrations within open-top chambers and ambient and elevated (+3°C) air temperatures. Measurements of photosynthesis and stomatal conductance were made throughout the experiments.
What was learned
Photosynthetic rates of both wheat and meadow fescue were 31-37% higher in the elevated CO2 treatment, while the average stomatal conductance of wheat was 23 and 27% lower in the elevated CO2 treatment at the ambient and elevated air temperatures, respectively, and the stomatal conductance of meadow fescue was 28 and 36% lower under the same circumstances.
What it means
With these significant CO2-induced increases in photosynthesis and decreases in stomatal conductance, we can expect the water use efficiencies of both spring wheat and meadow fescue to rise dramatically (from 70 to over 100%) as the CO2 content of the air over Finland (and elsewhere!) continues to rise. Also, we can expect these benefits to be greater at higher air temperatures.