Effect of Molecular Species of Leaf Cerebroside to Thermal Reactions in Crops

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1. Relationsphip between chilling sensitivity of plants and composition of cerebrosides was studied. Major molecular species of cerebrosides was isolated from higher plants by reversed phase HPLC and thermotropic behavior of them was analyzed by DSC. Phase transition temperature of cerebroside molecular species varied markedly with the geometrical isomers at the 8-unsaturation. In general, the cis-8-unsaturated species revealed low phase transition temperatures than the trans-8-unsaturated isomers.2. The chemical composition of leaf cerebrosides from higher plants was not very varied by varieties or growth stages. The cold acclimation resulted in a little change of cerebrosides composition from the chilling-sensitive plants, whereas those from the chilling-resistant plants were in a change of radish seedings and in a hard change of pea epicotyls. The cold acclimation resulted in an increase of the ratio of cerebrosides to glycerophospholipids from the chilling-resistant radish seedlings and pea epicotyls, but in a decrease or in a slight change of those from the chilling-sensitive squash and mung bean hypacotyls. The cold acclimation resulted in a slight unsaturation of the diacylglycerol moieteis from glycerophospholipids of both the chilling-resistant and chilling-sensitive plants. The molecular species of cerebrosides containing DELTA^<15> cis- unsaturated hydroxy fatty acids were observed in the chilling-resistant radish seedlings, but in chilling sensitive plants they were not detected.3. Membrane lipid composition changed remarkably with cold acclimation under the light growth conditions. The cold acclimation resulted in the increase of endoplasmic reticulum marker enzyme (NADH-cyy C reductase) activities and phosphatidic acid from chilling-sensitive mung bean hypocotyls.