Theoretical analysis of a temperature-dependent model of respiratory O2 consumption using the kinetics of the cytochrome and alternative pathways.

Temperature dependence of plant respiratory O2 -consumption has been empirically described by the Arrhenius equation. The slope of the Arrhenius plot (which is proportional to activation energy) sometimes deviates from a constant value. We conducted kinetic model simulations of mitochondrial electron flow dynamics to clarify factors affecting the shape of the Arrhenius plot. We constructed a kinetic model of respiration in which competitive O2 -consumption by the cytochrome pathway (CP) and the alternative pathway (AP) were considered, and we used this model to describe the temperature dependence of respiratory O2 -consumption of Arabidopsis. The model indicated that the electron partitioning and activation energy differences between CP and AP were reflected in the slope and magnitude of the dependent variables of the Arrhenius plot. When the electron partitioning and activation energies of CP and AP were constant with temperature change, our model suggested that the Arrhenius plot would be almost linear. When the electron partitioning or activation energy of CP, or both, rapidly changed with temperature, the Arrhenius plot deviated from linearity, as reported in previous experimental studies. Our simulation analysis quantitatively linked the kinetic model parameters with physiological mechanisms underlying the instantaneous temperature dependence of plant respiration rate.