EFFECTS OF MODERATELY ENHANCED LEVELS OF OZONE ON THE ACYL LIPID-COMPOSITION OF LEAVES OF GARDEN PEA (PISUM-SATIVUM)

Plants of garden pea (Pisum sativum L.) were exposed to charcoal-filte red air with or without addition of 65 +/- 5 nl l(-1) ozone. Plants we re harvested daily for 9 days and lipids were extracted from the secon d-oldest leaf. Visible injury of this leaf was evident from day 5 on, while the differences in lipids between ozone and control treatments w ere observed earlier. Ozone caused large decreases in the contents of monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG) and sulfoquinovosyldiacylglycerol (SQDG), a slower decrease in the co ntent of phosphatidylcholine (PC) but an increase in the content of ph osphatidylethanolamine (PE) per leaf area, compared with exposure to c harcoal-filtered air. The content of phosphatidylglycerol (PG) was una ffected by ozone. Compared with charcoal-filtered air, fumigation with ozone resulted in a decrease in the proportion of linolenic acid (18: 3) of the total lipid extract, with a concomitant increase in the prop ortion of linoleic acid (18:2). For individual lipids, ozone caused a similar pattern of decreased 18:3 and increased 18:2 in MGDG, SQDG, PC and PE, while the fatty acid composition of DGDG was unaffected. In P G, ozone decreased the proportions of 18:3 and trans-Delta(3)-decenoic acid (16:1(trans)), balanced by increased proportions of palmitic and oleic acids. The contents of chlorophylls and carotenoids were unaffe cted by ozone. Out results show that moderately elevated levels of ozo ne cause significant changes in the polar lipid composition of garden pea leaves and in the level of unsaturation of the lipid acyl groups a nd, furthermore, that ozone has different effects, which could be dire ct or indirect, on chloroplast Lipids (MGDG, DGDG, SQDG, PG acylated w ith 16:1(trans)) and cytosolic membrane lipids.