Table II. Isotopic and gas exchange values for a C₄ plant (amaranthus) based on light response measurements (compare, Fig. 4D).

¹⁸Δ^m and ¹⁸Δ^p are measured and predicted ¹⁸O discrimination (‰) when θ_eq = 1 and θ_eq = 0.6 (full or partial isotopic equilibrium, respectively), ε = C_cs/(C_a − C_cs) where C_a and C_cs indicate ambient and chloroplast surface CO₂ concentrations, Δ_ea is isotopic discrimination between atmospheric CO₂, δ_a, and that in equilibrium with leaf water, δ_e: Δ_ea = 1,000 × [(δ_e/1,000 + 1)/( δ_a/1,000 + 1) − 1]. Irradiance values are in μmol photon m⁻² s⁻¹. Analysis and definitions are based on Gillon and Yakir (2001).

Irradiance	18Δm	18Δp (θeq = 0.6)	18Δp (θeq = 1)	ε	Δea
171	30.2	30.35	48.87	0.95	35.55
352	31.1	31.58	51.10	1.00	31.25
524	23.35	23.62	36.93	0.72	31.30
1,179	16.95	17.26	25.54	0.45	32.78
1,889	3.77	10.20	14.20	0.18	34.59