Changes in membrane lipid and free fatty acid composition during low temperature preconditioning against SO2 injury in coleus

Abstract The effects of a low temperature (13 °C) treatment known to provide protection against sulphur dioxide (SO 2 ) injury were assessed on leaf lipid composition in two cultivars of Coleus blumei Benth, found previously to differ in sensitivity to SO 2 and other environmental stresses. After 5 days growth at 13 °C, there were significant differences in membrane lipid fatty acid composition as well as in free fatty acid (FFA) levels between SO 2 -sensitive ‘Buckley Supreme’ (‘BS’) and SO 2 -insensitive ‘Marty’ (‘M’). Molecular species of chloroplast galactolipids in ‘M’ contained increased levels of linolenic acid (18:3). In the leaf FFA pools, the saturated components, palmitic (16:0) and stearic (18:0) acids, were predominant at 20 °C. After temperature hardening at 13 °C, the total amount of FFAs decreased in ‘M’ but increased in ‘BS.’ These modifications in lipid composition suggest an additional mechanism for cultivar differences in tolerance to SO 2 and other stressors in coleus.