Three parameters comprehensively describe the temperature response of respiratory oxygen reduction

Using an exponential model that relies on Arrhenius kinetics, we explored Type I, Type II and dynamic (e.g. declining Q(10) with increasing temperature) responses of respiration to temperature. Our Arrhenius model provides three parameters: R(REF) (the base of the exponential model, nmol g(-1) s(-1)), E(0) (the overall activation energy of oxygen reduction that dominates its temperature sensitivity, kJ mol(-1)) and delta (that describes dynamic responses of E(0) to measurement temperature, 10(3) K(2)). Two parameters, E(0) and delta, are tightly linked. Increases in overall activation energy at a reference temperature were inversely related to changes in delta. At an E(0) of ca. 45 kJ mol(-1), delta approached zero, and respiratory temperature response was strictly Arrhenius-like. Physiologically, these observations suggest that as contributions of AOX to combined oxygen reduction increase, E(0)(REF) decreases because of different temperature sensitivities for V(max), and delta increases because of different temperature sensitivities for K(1/2) of AOX and COX. The balance between COX and AOX activity helps regulate plant metabolism by adjusting the demand for ATP to that for reducing power and carbon skeleton intermediates. Our approach enables determination of respiratory capacity in vivo and opens a path to development of process-based models of plant respiration.