Aerobic respiration rate of Golden Delicious apples as a function of temperature and PO-2

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, O(2) consumption (r(o2)) and CO(2) production (r(co2)) rates were measured at four temperatures (21, 16, 6 and 1 degrees C) and five partial pressures of O(2) (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 O(2) by a Michaelis-Menten-like equation. The maximum rate of O(2) consumption (k(2)) increased linearly with temperature and the Michaelis constant K(M) decreased according to Arrhenius' equation. The activation energy calculated for k(2) (Delta E(2)/R = 5097 degrees K(-1)) is very close to that found using a different theoretical approach (Delta E(2)/R = 5447 degrees 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 degrees C when a P(co2) value close to zero was maintained. (C) 1998 Elsevier Science B.V. All rights reserved.