Effect of Copper on Fatty-Acid Composition and Peroxidation of Lipids in the Roots of Copper Tolerant and Sensitive Silene-Cucubalus.

Abstract

The effect of high copper exposure in vivo on the lipid and fatty acid composition and lipid peroxidation was studied in the roots of plants from one copper sensitive and two copper tolerant genotypes of Silene cucubalus. At 0.5 muM Cu (control treatment) the compositions of lipids and fatty acids in sensitive plants were not different from those in tolerant plants. An exposure to 20 muM Cu for 3 days (high copper treatment) caused a significant decrease in the fatty acid content and a shift in the composition of fatty acids resulting in a lower degree of fatty acid unsaturation in the sensitive plants only. The high copper treatment did not affect the lipid and fatty acid compositions in the intermediately tolerant plants, and increased the fatty acid content in the most tolerant plants. When sensitive and tolerant genotypes were exposed to a range of copper concentrations, lipid peroxidation was only observed at those concentrations that were toxic for that genotype. Lipoxygenase (EC 1.13.11.12) was apparently not active in the roots, suggesting that lipid peroxidation was initiated by copper itself, rather than through activation of lipoxygenase. The results indicate that (a) copper toxicity involves the peroxidative degradation of unsaturated fatty acids, and (b) the mechanism of copper tolerance in S. cucubalus does not rely on a constitutive change in the lipid and fatty acid composition of the roots.