Table 1.

Leaf traits and photosynthetic parameters of wheat (T. aestivum) and sunflower (H. annuus) grown under ambient or elevated CO₂ (aCO₂ or eCO₂)

	T. aestivum		H. annuus		Significance
	aCO2	eCO2	aCO2	eCO2	spe	CO2	spe × CO2
A growth	28.42 ± 0.73	32.79 ± 2.01	27.27 ± 2.57	31.43 ± 2.06	0.529	0.042	0.956
A max	37.68 ± 1.29	34.04 ± 2.22	32.32 ± 2.40	31.83 ± 1.73	0.068	0.304	0.430
R Dk	2.26 ± 0.14	1.81 ± 0.17	1.48 ± 0.11	1.32 ± 0.14	<0.001	0.046	0.327
iWUEgrowth	52.64 ± 1.30	62.25 ± 3.94	37.30 ± 10.25	102.14 ± 24.99	0.380	0.013	0.057
SLA	0.24 ± 0.01	0.27 ± 0.02	0.22 ± 0.02	0.23 ± 0.02	0.038	0.252	0.511
N%	6.61 ± 0.17	6.39 ± 0.11	3.51 ± 0.67	3.16 ± 0.56	<0.001	0.527	0.882
Narea	2.70 ± 0.06	2.37 ± 0.10	1.53 ± 0.18	1.35 ± 0.16	<0.001	0.062	0.586
Chl	0.69 ± 0.02	0.56 ± 0.03	0.49 ± 0.05	0.48 ± 0.02	<0.001	0.04	0.083
V cmax	160.9 ± 3.2	142.7 ± 13.0	123.0 ± 11.7	117.4 ± 3.3	0.002	0.203	0.493
J	183.4 ± 3.3	160.1 ± 9.3	164.2 ± 10.4	158.9 ± 8.6	0.234	0.101	0.293
g sc/gm	0.95 ± 0.03	1.16 ± 0.07	1.74 ± 0.55	1.97 ± 0.42	0.087	0.222	0.859
CUEL	0.89 ± 0.01	0.92 ± 0.01	0.92 ± 0.02	0.94 ± 0.01	0.011	0.004	0.547

Leaf trait parameters include: specific leaf area (SLA, cm² mg⁻¹), leaf nitrogen content per dry mass (N%), leaf nitrogen content per area (N_area, g m⁻²), chlorophyll content (Chl, g m⁻²). Photosynthetic parameters include net CO₂ assimilation rate at the growth CO₂ (A_growth, μmol m⁻² s⁻¹), maximum CO₂ assimilation rate (A_max, μmol m⁻² s⁻¹), respiration rate in the dark (R_Dk, μmol m⁻² s⁻¹), intrinsic water-use efficiency (iWUE_growth, μmol mol⁻¹), maximum carboxylation rates by Rubisco (V_cmax, μmol m⁻² s⁻¹), electron transport rate (J, μmol m⁻² s⁻¹), the ratio of stomatal conductance for CO₂ to mesophyll conductance (g_sc/g_m), leaf carbon-use efficiency (CUE_L). Data are mean ± SE (n = 6); significant treatment effects (P < 0.05) tested with two-way ANOVAs are shown in bold.