Table 4.

Leaf dark respiration rates (R_d) at 30 °C and ¹³CO₂ composition of dark-evolved CO₂ (δ¹³C_Rd) determined on gdch-KD versus the WT after 6 min [R_d(6min) and δ¹³C_Rd(6min); n=4], 30 min [R_d(30min) and δ¹³C_Rd(30min); n=4], 3 h [R_d(3h) and δ¹³C_Rd(3h); n=4], and 24 h [R_d(24h) and δ¹³C_Rd(24h); n=3] in the dark following leaf exposure to light under approximately current ambient and below current ambient O₂ levels (pO₂ of 18.4 kPa and 1.84 kPa, respectively)

Plant-type	pO2	R d(6min)	δ13CRd(6min)	R d(30min)	δ13CRd(30min)	R d(3h)	δ13CRd(3h)	R d(24h)	δ13CRd(24h)
	(kPa)	(µmol CO2 m-2 s-1)	(‰)	(µmol CO2 m−2 s−1)	(‰)	(µmol CO2 m−2 s−1)	(‰)	(µmol CO2 m−2 s−1)	(‰)
gdch-KD	1.84	1.48±0.05	−39.2±0.9*	1.04±0.06	−47.3±1.6*	0.81±0.04	−56.0±0.7*	0.79±0.02	−58.0±0.5*
WT	1.84	1.23±0.04	−40.6±1.2*	1.04±0.01	−47.2±1.7*	0.77±0.04	−54.1±0.7*	0.69±0.02	−58.6±1.0*
Significance								P=0.045	P=0.705
gdch-KD	18.4	2.59±0.29	−45.6±1.7	1.98±0.20	−54.1±0.9	1.34±0.17	−55.6±1.2	0.69±0.06	−58.1±0.1
WT	18.4	2.13±0.07	−43.2±0.9	1.47±0.08	−50.4±2.8	1.12±0.13	−52.5±1.8	0.74±0.08	−58.6±0.6
Significance	Plant type	P=0.042	P=0.723	P=0.110	P=0.349	P=0.215	P=0.132	P=0.596	P=0.410
	pO2	P=0.0001	P=0.032	P=0.0009	P=0.035	P=0.004	P=0.429	–	–
	Plant type×pO2	P=0.407	P=0.238	P=0.069	P=0.375	P=0.326	P=0.753	–

Values are the mean ±SE; the asterisks indicate means from δ¹³C_Rd values edited according to Supplementary Method S7. Significance (P<0.05) of the effects of plant type, pO₂, and plant type×pO₂ interaction was evaluated by SAS PROC MIXED. The effect of plant type on R_d(24h) and δ¹³C_Rd(24h) was evaluated at a pO₂ of 1.84 kPa or 18.4 kPa by one-way ANOVA (significance for P<0.05).