Wheat Mitochondria

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Abstract
Mitochondrial oxidative activity and membrane lipid structure of 2 wheat (Triticum aestivum L.) cultivars were measured as a function of temperature. The Arrhenius activation energy for the oxidation of succinate and .alpha.-ketoglutarate was constant over the temperature range of 3-27.degree. C. The activation energy for succinate-cytochrome c oxidoreductase [EC 1.3.99.1] activity was 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 3 spin-labeling techniques, wheat membrane lipids were shown to undergo phase changes at about 0.degree. C and 30.degree. C. Apparently the membrane lipids of wheat, a chilling resistant plant, undergo a phase transition similar to the transition observed in the membrane lipids of chilling-sensitive plants. For wheat the transition is initiated at a lower temperature and extends over a wider temperature range.