TABLE 5.

Fitted (Eq. 10) and measured (Obs.) values of parameters defining the light response curve of instantaneous water-use efficiency for C₃ (soybean) and C₄ species (grain amaranth).

Species	α2		WUEinst–max (μmol mmol–1)		Iinst–sat (μmol m–2 s–1)		β2 (m2 s μmol–1)		γ2 (m2 s μmol–1)		Kinst (μmol mmol–1)
	Eq. 10	Obs.	Eq. 10	Obs.	Eq. 10	Obs.	Eq. 10	Obs.	Eq. 10	Obs.	Eq. 10	Obs.
Soybean	0.035 ± 0.006a	–	2.42 ± 0.17b	2.47 ± 0.16b	1182.74 ± 63.01a	1300.00 ± 191.49a	(9.38 ± 1.29) × 10–5	–	(6.34 ± 0.82) × 10–3	–	1.78 ± 0.19a	1.80 ± 0.19a
Grain amaranth	0.037 ± 0.008a	–	6.99 ± 0.50a	7.03 ± 0.52a	1649.05 ± 260.38a	1300.00 ± 100.00a	(1.21 ± 0.32) × 10–4	–	(2.83 ± 0.83) × 10–3	–	1.81 ± 0.24a	2.24 ± 0.32a

The parameters are initial slope of the WUE_inst-I curve (α₂), coefficients β₂ and γ₂ and K_inst, the maximum instantaneous water-use efficiency (WUE_inst–max), and the corresponding saturation irradiance (I_inst–sat). All values are the means ± SE (n = 4). Different letters denote statistically significant differences (P ≤ 0.05) between soybean and grain amaranth within each column of fitted (Eq. 10) or measured (Obs.) values. There is no statistically significant difference between fitted (Eq. 10) and measured (Obs.) values for each parameter. See Table 1 for definitions of abbreviations.