Plant Physiology 59:623-627 (1977)
© 1977 American Society of Plant Biologists
Articles
Wheat Mitochondria
Oxidative Activity and Membrane Lipid Structure as a Function of Temperature
John K. Raison,
Elza A. Chapman and
P. Y. White
1 Plant Physiology Unit, CSIRO Division of Food Research and School of Biological Sciences, Macquarie University, North Ryde, N.S.W. 2113, Australia
Mitochondrial oxidative activity and membrane lipid structure of two wheat (Triticum aestivum L.) cultivars were measured as a function of temperature. The Arrhenius activation energy for the oxidation of both succinate and  -ketoglutarate was constant over the temperature range of 3 to 27 C. The activation energy for succinate-cytochrome c oxidoreductase activity was also constant over the same temperature range. The concentration of mitochondria in the reaction, the degree of initial inhibition of state 3 respiration, and the time after isolation of mitochondria were each shown to be capable of causing a disproportionate decrease in the rate of oxidation at low temperatures which resulted in an apparent increase in the activation energy of oxidative activity. Using three spin-labeling techniques, wheat membrane lipids were shown to undergo phase changes at about 0 C and 30 C. It is concluded that the membrane lipids of wheat, a chillingresistant plant, undergo a phase transition similar to the transition observed in the membrane lipids of chilling-sensitive plants. For wheat, however, the transition is initiated at a lower temperature and extends over a wider temperature range.
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