Journal
PLANT CELL AND ENVIRONMENT
Volume 31, Issue 7, Pages 901-914Publisher
WILEY
DOI: 10.1111/j.1365-3040.2008.01808.x
Keywords
energy balance; respiratory quotient (CO2/O-2); temperature response of growth
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We showed that temperature responses of dark respiration for foliage of Pinus radiata could be approximated by Arrhenius kinetics, whereby E-0 determines shape of the exponential response and denotes overall activation energy of respiratory metabolism. Reproducible and predictable deviation from strict Arrhenius kinetics depended on foliage age, and differed between R-CO2 and R-O2. Inhibition of oxygen reduction (R-O2) by cyanide (inhibiting COX) or SHAM (inhibiting AOX) resulted in reproducible changes of the temperature sensitivity for R-O2, but did not affect R-CO2. Enthalpic growth - preservation of electrons in anabolic products - could be approximated with knowledge of four variables: activation energies (E-0) for both R-CO2 and R-O2, and basal rates of respiration at a low reference temperature (R-REF). Rates of enthalpic growth by P. radiata needles were large in spring due to differences between R-REF of oxidative decarboxylation and that of oxygen reduction, while overall activation energies for the two processes were similar. Later during needle development, enthalpic growth was dependent on differences between E-0 for R-CO2 as compared with R-O2, and increased E-0(R-O2) indicated greater contributions of cytochrome oxidase to accompany the switch from carbohydrate sink to source. Temperature-dependent increments in stored energy can be calculated as the difference between R-CO2 Delta H-CO2 and R-O2 Delta H-O2.
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