Aerobic respiration rate of Golden Delicious apples as a function of temperature and PO2

To evaluate the temperature dependence of the constants involved in a mathematical model relating the aerobic respiration rate of Golden Delicious apples to the P(O2) of the surrounding atmosphere, O2 consumption (r(O2)) and CO2 production (r(CO2)) rates were measured at four temperatures (21, 16, 6 and 1°C) and five partial pressures of O2 (0, 3, 5, 10 and 21 kPa), while P(CO2) was maintained close to zero. The cellular oxidation of the respiratory substrate was expressed as a function of dissolved O2 by a Michaelis-Menten-like equation. The maximum rate of O2 consumption (k2) increased linearly with temperature and the MichaeliS constant K(M) decreased according to Arrhenius' equation. The activation energy calculated for k2 (ΔE2/R = 5097°K-1)is very close to that found using a different theoretical approach (ΔE2/R = 5447°K-1). The temperature dependence of these constants made it possible to individuate a mathematical model able to calculate, as a function of the P(O2), the aerobic respiration rate expected for Golden Delicious apples stored between 0 and 20°C when a P(CO2) value close to zero was maintained.