Table I.

Rates of respiration and maximum photosynthesis in N. sylvestris WT and the CMSII mutant

MeasurementWTCMSII
μmol m−2 leaf surface s−1
Photosynthetic O2evolution33.1 ± 2.036.4 ± 3.8
Respiratory O2consumption1.29 ± 0.292.14 ± 0.48
Respiratory CO2 evolution1.12 ± 0.181.87 ± 0.16

Oxygen exchange was measured in a leaf disc oxygen electrode, where CO2 is maintained at saturating partial pressure (approximately 30 mbar). To drive maximum rates of photosynthetic O2 evolution, irradiance was 1,400 μmol m−2s−1. O2 exchange data are means ±se of three leaf discs, each from a different plant. CO2 release was measured in attached leaves by infrared gas analysis at 350 μbar CO2, 20 min after introduction of the leaf into the chamber and darkening. CO2 evolution data are means ± se of 18 (WT) and 10 (CMSII) measurements of attached leaves.