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Photosynthesis and photorespiration rates at the CO 2 compensation point

1970; Canadian Science Publishing; Volume: 48; Issue: 6 Linguagem: Inglês

10.1139/b70-189

1480-3305

N. R. Bulley, E. B. Tregunna,

Atmospheric and Environmental Gas Dynamics

Attached soybean leaves in a closed system were fed high specific activity 14 CO 2 at four CO 2 compensation points (30, 53, 110, 204 μl/l CO 2 ) which were produced by different O 2 concentrations (10, 21, 44, 80% O 2 ). Rates of CO 2 uptake and evolution were measured simultaneously using an infrared CO 2 gas analyzer and a Geiger tube. The CO 2 compensation point was proportional to O 2 concentration but did not change for the two light intensities used. The rates of CO 2 exchange at the compensation point did increase with light intensity. These rates of CO 2 exchange also increased with the increasing CO 2 concentration of the compensation point (for increasing O 2 concentrations) but tended to saturate for compensation points greater than 110 μl/l CO 2 .