Table I.

Leaf gas-exchange measurements

The rates of net CO₂ assimilation and stomatal conductance in air (373 μbar) and elevated (1,515 μbar) CO₂ concentrations and the Γ in wild-type plants, peroxisomal NAD⁺-malate dehydrogenase 1 and 2 plants (pmdh1 and pmdh2, respectively), and double pmdh1pmdh2 T-DNA mutants of Arabidopsis. Gas-exchange measurements were made at a pO₂ of 200 mbar, irradiance of 500 μmol quanta m⁻² s⁻¹, and leaf temperature of 25°C. Values of Γ were inferred from the initial slope of a CO₂ response curve at lowest CO₂ concentrations. Shown are means ± se of measurements made on three to five leaves from separate plants. Statistical analysis was conducted using ANOVA, and different letters indicate significant differences between plants at P < 0.05.

Variable	Wild Type	pmdh1	pmdh2	pmdh1pmdh2
Net CO2 assimilation rate (μmol CO2 m−2 s−1)
Air	10.6 ± 1.1 a	9.9 ± 1.3 a	8.2 ± 1.3 a,b	6.9 ± 0.4 b
Elevated CO2	17.5 ± 1.4 a	17.2 ± 2.6 a	14.5 ± 2.9 a	15.2 ± 1.0 a
Stomatal conductance (mmol m−2 s−1)
Air	0.20 ± 0.02 a	0.20 ± 0.02 a	0.15 ± 0.02 b	0.20 ± 0.01 a
Elevated CO2	0.21 ± 0.03 a	0.17 ± 0.03 a	0.13 ± 0.01 b	0.19 ± 0.02 a
Γ (μbar)	59 ± 5 a	65 ± 3 a	81 ± 1 a	109 ± 9 b