Influence of winter and summer growth conditions on leaf membrane lipids of Pisum sativum L.

The lipid composition and degree of unsaturation of fatty acids has been measured for membranes isolated from leaves of Pisum sativum grown under either summer or winter conditions. Although the lipid-class composition was not significantly changed for the two growth conditions the degree of unsaturation of the fatty acids was greater for winter than summer plants. The difference in unsaturation was evident with all lipid classes of the non-thylakoid membranes including the galactolipids of the chloroplast envelope. In contrast, both the relative amounts of lipid classes and degree of saturation were not greatly changed for summer and winter thylakoids with the exception that phosphatidylglycerol had a greater linolenic acid (18:3) content for the thylakoids of winter grown leaves. However, a striking difference was found for the total acyl lipid to chlorophyll ratio for thylakoids isolated from summer or winter plants, with the former producing a lower ratio than the latter growth conditions. The above changes in lipid composition of chloroplast membranes are discussed in terms of optimizing their functional activities under the different growth conditions.