Structural and functional responses of wheat mitochondrial membranes to growth at low temperatures.

The responses in membrane lipid composition, structure, and function of four cultivars of wheat (Triticum aestivum L.) to growth at low temperature have been investigated. Marked growth temperature-dependent alterations in the fatty acid composition and unsaturation of the mitochondrial phospholipids correlate with changes in respiratory activity in all the varieties. Parameters such as the respiratory control ratio and the phosphorylative efficiency decrease in cold-adapted seedlings. Three temperature-dependent structural transitions were identified in the mitochondria by the spin-labeling method. The structural transitions occur at lower temperatures in the cold-grown material. The shift in one transition appears to be quantitatively greater in the winter hardy varieties. Cold-induced changes in all of the other measured parameters were indistinguishable in hardy and nonhardy varieties. The results indicate major involvement of the phospholipid matrix in cold acclimation. A link between cold acclimation and winter survival may exist involving the structural and functional modifications in membrane structure which occur during acclimation.