Temperature response of parameters of a biochemically based model of photosynthesis. II. A review of experimental data

The temperature dependence of C₃ photosynthesis is known to vary with growth environment and with species. In an attempt to quantify this variability, a commonly used biochemically based photosynthesis model was parameterized from 19 gas exchange studies on tree and crop species. The parameter values obtained described the shape and amplitude of the temperature responses of the maximum rate of Rubisco activity (V_cmax) and the potential rate of electron transport (J_max). Original data sets were used for this review, as it is shown that derived values of V_cmax and its temperature response depend strongly on assumptions made in derivation. Values of J_max and V_cmax at 25°C varied considerably among species but were strongly correlated, with an average J_max: V_cmax ratio of 1.67. Two species grown in cold climates, however, had lower ratios. In all studies, the J_max:V_cmax ratio declined strongly with measurement temperature. The relative temperature responses of J_max and V_cmax were relatively constant among tree species. Activation energies averaged 50 kJ mol^-1 for J_max and 65 kJ mol^-1 for V^cmax, and for most species temperature optima averaged 33°C for J_max and 40°C for V_cmax. However, the cold climate trees pecies had iow temperature optima for both J_max (19°C) and V_cmax (29°C), suggesting acclimation of both processes to growth temperature. Crop species had somewhat different temperature responses, with higher activation energies for both J_max and V_cmax, implying narrower peaks in the temperature response for these species. The results thus suggest that both growth environment and plant type can influence the photosynthetic response to temperature. Based on these results, several suggestions are made to improve modelling of temperature responses.