Photosynthesis and photorespiration rates at the CO2compensation point

摘要

Attached soybean leaves in a closed system were fed high specific activity14CO2at four CO2compensation points (30, 53, 110, 204ensp;mu;l/l CO2) which were produced by different O2concentrations (10, 21, 44, 80 O2). Rates of CO2uptake and evolution were measured simultaneously using an infrared CO2gas analyzer and a Geiger tube. The CO2compensation point was proportional to O2concentration but did not change for the two light intensities used. The rates of CO2exchange at the compensation point did increase with light intensity. These rates of CO2exchange also increased with the increasing CO2concentration of the compensation point (for increasing O2concentrations) but tended to saturate for compensation points greater than 110ensp;mu;l/l CO2.