TABLE 2.

Summary of gas exchange and biochemical data for three Nytaginaceae species.

Parameter	Nyctaginia capitata	Boerhavia coccinea	Allionia incarnata	C4 p value (one-tailed)
Net CO2 assimilation rate at 400 μmol CO2 mol–1 air, in μmol m–2 s–1	7.0	23.0 ± 2.1	26.8 ± 0.9	0.08
Net CO2 assimilation rate at 1200 μmol CO2 mol–1 air, in μmol m–2 s–1	23.5	31.3 ± 0.7	30.5 ± 1.5	0.32
A400/A1200	0.30	0.74 ± 0.06	0.88 ± 0.03	0.04
A/gs, mmol CO2 mol–1 H2O	100	158 ± 3	149 ± 5	0.10
Ci/Ca	0.58	0.31 ± 0.01	0.35 ± 0.02	0.10
Initial slope of the A vs Ci curve, mol m–2 s–1	0.05	0.25 ± 0.03	0.36 ± 0.04	0.04
Initial slope/A1200	0.002	0.008 ± 0.001	0.012 ± 0.001	0.03
CO2 compensation point of A, μmol mol–1	75	4.5 ± 0.5	2.5 ± 1.0	0.06
PEP carboxylase activity, μmol m–2 s–1	15.1 ± 1.9	111.8 ± 7.9	131.7 ± 22.2	0.22
PEP carboxylase activity, mmol mol–1 CHL s–1	27.0 ± 2.7	261.9 ± 12.4	429.7 ± 53.2	0.01
NADP-ME activity, μmol m–2 s–1	0 ± 0	50.1 ± 5.6	0 ± 0	< 0.001
NADP-ME activity, mmol mol–1 CHL s–1	0 ± 0	116.7 ± 8.9	0 ± 0	< 0.001
NAD-ME activity, μmol m–2 s–1	0 ± 0	2.1 ± 0.6	27.7 ± 2.8	< 0.001
NAD-ME activity, mmol mol–1 CHL s–1	0 ± 0	5.1 ± 1.4	91.5 ± 6.4	< 0.001
Chlorophyll, mmol m–2	0.56 ± 0.02	0.43 ± 0.02	0.30 ± 0.01	< 0.001
Chlorophyll a/b ratio	3.46 ± 0.07	4.45 ± 0.09	3.67 ± 0.08	< 0.001

Means ± SE, N = 4 for the C₄ species, 1 for N. capitata gas exchange data, and 3 for N. capitata biochemical data. The p-values of one-tailed Students T-tests between the two C₄ species are indicated, with significant differences highlighted in bold. Gas exchange measurements were conducted at 33°C and a light intensity of 1800 μmol m^–2 s^–1. Biochemical assays were conducted at 30°C. A, net CO₂ assimilation rate; C_i, intercellular CO₂ concentration; C_a, ambient CO₂ concentration in the leaf chamber; A₄₀₀, A at a CO₂ concentration of 400 μmol CO₂ mol^–1 air; A₁₂₀₀, A at a CO₂ concentration of 1200 μmol mol^–1; CHL, leaf chlorophyll content; g_s, leaf conductance to water vapor; ME, malic enzyme.