Abstract
Changes in the content of polar lipids and in their fatty acid composition in spinach leaves during storage were studied in order to clarify the mechanism of leaf-yellowing.
The total glycolipids, particularly monogalactosyldiglyceride (MGDG) and diga-lactosyldiglyceride (DGDG), decreased markedly during storage at 25°C. The total phospholipids, however, decreased moderately during storage at 25°C, the decrease in phosphatidylglycerol (PG) being the most notable.
In the chloroplast lipids (MGDG, DGDG and PG), the relative amounts of hexadecatrienoic acid in MGDG, and palmitoleic acid and linolenic acid in PG decreased during storage at 25°C. Conversely, the relative amount of linoleic acid in MGDG, DGDG and PG increased. The percentage of unsaturated fatty acids in all the polar lipids, however, showed hardly any change.
From these results, it is inferred that the degradation of chlorophylls may be caused by the hydroperoxides of free fatty acids which have been formed by the degradation of polar lipids such as MGDG, DGDG and PG.
