IN-SITU LEAF LIPID-METABOLISM IN GARDEN PEA (PISUM-SATIVUM L) EXPOSEDTO MODERATELY ENHANCED LEVELS OF OZONE

The effects of ozone on the lipid metabolism of garden pea (Pisum sati vum L.) was investigated in two experimental designs, To study the eff ects on lipid biosynthesis, pea plants were exposed for 3 d to < 5 nl l(-1) ozone or to 65 +/- 5 nl l(-1) ozone (12 h d(-1)), before labelli ng with [1 - C-14]acetate. To study the effects on lipid degradation, pea plants were exposed to (CO2)-C-14 for 2 h, After 3 d, when the dis tribution of radioactivity between lipid classes had approached the ma ss distribution of lipids, the plants were exposed to different levels of ozone as above, Distribution of radioactivity between lipid classe s was monitored daily for 6-9 d. The results show that 65 nl l(-1) ozo ne caused significant alterations in lipid metabolism. The major effec ts of ozone fumigation of garden pea were stimulated degradation of th e chloroplast lipids monogalactosyldiacylglycerol (MGDG) and digalacto syldiacylglycerol (DGDG); increased synthesis of phosphatidylethanolam ine (PE); decreased synthesis of some wax components and an unknown no n-polar lipid (probably associated with a light membrane fraction); an d induced synthesis of another unknown non-polar lipid, associated wit h the cuticle and/or chloroplasts. Thus, the effects of ozone on plant lipid metabolism were widespread in the cell and indicate that ozone has direct and/or indirect effects on several membrane systems. It is noteworthy that ozone affected acyl lipids of chloroplasts and non-chl oroplast membranes differently. The results of the present investigati on partly differs from those obtained by other investigators. These di screpancies and the implications of the obtained results on plant memb rane structure and function are discussed.