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Influence of Episodes of Summer O3 on Δ5 and Δ9 Fatty Acids in Autumnal Lipids of Norway Spruce [Picea abies (L.) Karst]
Alan R. Wellburn, Deborah C. Robinson, Alan Thomson and Ian D. Leith
The New Phytologist
Vol. 127, No. 2 (Jun., 1994), pp. 355-361
Stable URL: http://www.jstor.org/stable/2558035
Page Count: 7
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Current year needles from 5 yr-old Norway spruce trees, which had been exposed to either episodes of atmospheric O3 or periodic mistings with simulated acid rainwater throughout three summer periods, were analyzed for changes in molar percentages and ratios of fatty acids isolated from different lipids at the time of maximum winter hardening. No significant changes due to acidic mistings were detected but significant decreases in the degree of unsaturation of both C16 and C18 fatty acids, the molar percentage of Δ5,9,12,1518:4, and the molar ratio of Δ5,918:2 to Δ9,1218:2 in monogalactosyl diglyceride (MGDG) due to summer O3 exposures were found. Molar percentages and ratios of fatty acids did not change much in other lipids but these changes in plastidic MGDG could be traced to a significant effect of summer O3 on the Δ5- and Δ12-desaturases acting upon phosphatidyl choline (PC) in the endoplasmic reticulum. The replacement of the Δ6-subset of C18 fatty acids by an equivalent Δ5-series throughout was confirmed by gas chromatography and mass spectrometry. Molecular modelling also showed that the Δ5-forms, which resembled the Δ9-isomers, are very different in shape to the Δ6-series and this may account, in part, for the extremely low winter temperatures from which Norway spruce needles may recover.
The New Phytologist © 1994 New Phytologist Trust