Mass spectrometric study of the kinetics of O2 consumption and CO2 production by breathing leaves

Camellia Japonica leaves are used as samples for studying respiration rates by a quantitative method of measurement at accurately controlled temperatures in the –3 to +30 °C range. O2 consumption and CO2 production are analyzed by a quadrupole mass spectrometer in a high vacuum chamber. It was found that for aerobic respiration the stoichiometric transformation of O2 into CO2 follows pseudo-first-order kinetics, with a reaction rate constant which at 20 °C is of k = 0.080 ± 0.003 days−1 for 93 g of wet leaves. Measurements, when analyzed according to an Arrhenius-like behaviour, lead to an activation energy of 85 ± 8 kJ mol−1, but a pronounced (convex or super-Arrhenius) deviation is observed.