Fig. 2.

Temperature effects on enzyme-driven processes of photosynthesis. (A) Schematic energy profile of an exergonic chemical reaction. Enzymes, such as Rubisco, facilitate biochemical reaction progression by lowering the activation energy requirements of the transition state between reactants and product formation, though in the case of Rubisco this is simplified as the enzyme facilitates a multistep catalysis (Flamholz et al., 2019). (B) Modelled temperature responses of tobacco Rubisco carboxylation catalytic turnover rate (green solid) and specificity for CO₂ over O₂ (yellow dashed line), using parameters from Orr et al. (2016) and temperature responses from Bernacchi et al. (2001). (C) Temperature response of gross photosynthesis (carbon assimilation A+mitochondrial respiration R_d, green solid line) and of mitochondrial respiration (R_d, gold dotted line) for an idealized C₃ species. Data were modelled using the leaf model of photosynthesis (Farquhar et al., 1980) with temperature adjustments (Bernacchi et al., 2001).