Table III.

The effect of low O2 on photosynthesis, transpiration, and Gly/Ser in WT and CMSII leaves

PlantWTWTCMSIICMSII
O2(mbar)2102021020
A (μmol m−2s−1)13.9 ± 0.619.6 ± 1.89.9 ± 1.416.3 ± 1.6
O2 stimulation of A (%)4165
1,000× A/Transpiration8.2 ± 0.811.3 ± 1.78.6 ± 0.811.6 ± 0.7
Gly/Ser4.18 ± 0.691.31 ± 0.542.42 ± 0.190.43 ± 0.03

Attached leaves from four WT or CMSII plants were illuminated at an irradiance of 700 μmol m−2 s−1 and 350 μbar CO2, 210 mbar O2 to induce photosynthesis (30-min illumination). Oxygen was either maintained at 210 mbar or decreased to 20 mbar. After a further 30-min illumination, CO2 uptake (A) and transpiration were measured, then metabolism was rapidly quenched in the incubated portion of the leaf by freeze clamping. Gly and Ser were extracted and determined by HPLC. Data are means ± se.