Effects of Temperature on Electron Transport in Arum maculatum Mitochondria.

The effects of temperature upon the respiratory pathways of Arum maculatum mitochondria have been studied. The alternate oxidase sustained a greater proportion of the total respiration at low temperatures than at higher temperatures. Arrhenius plots of respiratory activities show two discontinuities, one at 14 degrees C and one at 21 degrees C. The lower temperature discontinuity was associated with electron transport from succinate dehydrogenase to the alternative oxidase, enzymes that face the inner side of the membrane while the higher temperature discontinuity was associated with electron transport from the external NADH dehydrogenase to cytochrome c oxidase, which face the outer side of the membrane. Both discontinuities resulted in a decrease in the activation energy for electron transport on one side of the membrane. Arrhenius plots of transmembrane electron transport showed discontinuities at both 14 degrees and 21 degrees C but the upper discontinuity resulted in an increase in the activation energy. Activation energies determined for the respiratory activities show that above 21 degrees C the exogenous NADH-cytochrome pathway and the succinate-alternative oxidase pathway were lower than those for the NADH-alternative pathway or the succinate cytochrome pathway.