Figure 5.

Temperature response of PEPc parameters in S. viridis compared with corresponding temperature responses from the literature normalized to S. viridis at 25°C. The V_pmax (A), K_P (B), and v_p (C) were measured on crude leaf extracts with membrane inlet mass spectrometry. Calculations of K_P assumed a constant leaf pH of 7.2 and a pKa appropriate for an ionic strength or 0.1 m (Jenkins et al., 1989), with a temperature dependency as described by Harned and Bonner (1945). The model of v_p used a measured V_pmax of 450 μmol m⁻² s⁻¹ at 25°C and a constant mesophyll pCO₂ of 12 Pa. The solid lines are the modeled temperature responses from this report (Table I), with 95% confidence intervals in gray. Dotted lines are the temperature responses for V_pmax for maize (Massad et al., 2007) and for K_P (Chen et al., 1994) normalized to S. viridis at 25°C. Black circles are the means of three biological replicates ± se, and the white circle in B is the K_P reported previously for maize ± se (Bauwe, 1986). P values refer to the significance of the temperature response from zero, and adjusted R² values describe the amount of variation in the measured parameter explained by the model.