Table 1.

Observed and optimal V_cmax/J_max ratios for soya bean grown at elevated [CO₂], air temperature or both and associated predicted reductions in canopy productivity. (Observed parameter values were obtained from [25]. Results are shown for two contrasting field seasons in Illinois: 2009 (cool) and 2011 (hot).)

year	[CO2] (Pa)	monthly average T (°C)	ΔT (°C)	observed Vcmax/Jmax	optimal Vcmax/Jmax	predicted canopy productivity with observed Vcmax/Jmax ratio (kg CH2O m−2 d−1)	predicted canopy productivity with optimal Vcmax/Jmax ratio (kg CH2O m−2 d−1)	relative productivity difference optimal versus observed Vcmax/Jmax ratio (%)
2009	38.5	21.3	0	0.63	0.47	383	421	10
2009	38.5	21.3	3.5	0.72	0.54	399	446	12
2009	58.5	21.3	0	0.63	0.40	453	525	16
2009	58.5	21.3	3.5	0.66	0.44	513	590	15
2011	38.5	27.2	0	0.79	0.60	397	448	13
2011	38.5	27.2	3.5	0.81	0.72	395	411	4
2011	58.5	27.2	0	0.71	0.48	541	623	15
2011	58.5	27.2	3.5	0.79	0.57	559	640	14