• Direct inhibition of dark respiration by elevated atmospheric concentrations of CO2 could alter the carbon balance of plants and ecosystems. The short-term response of leaf dark respiration to elevated CO2 concentrations are reported here in 12 grass and forb species of a North American grassland community.
• Specific respiration rates at 25°C and a range of measurement CO2 concentrations were determined for detached leaves of each species field-grown in monoculture.
• On average, respiration rates were 1.8% lower at 700 than at 360 µmol mol−1 CO2. Among species, responses ranged from a 6.4% inhibition to a 2.4% stimulation and were generally not statistically significant. Across a range of CO2 concentrations from 360 to 1300 µmol mol−1, respiration rates declined linearly and were 11% lower at 1300 than 360 µmol mol−1 CO2.
• Direct inhibition of leaf respiration is small compared with other longer-term, indirect effects of CO2 on carbon exchange. The direct effects of rising atmospheric CO2 concentrations on respiration rates should result in minimal effects on plant carbon exchange in grasslands.