ABSTRACT
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 misting were detected but significant decreases in the degree of unsaturation off both C 16 and C18 , fatty acids, the molar percentage of δ5,9,12,15 , and the molar ratio δ5,9 18: 2 to δ9,12 18:2 in monogalactosyl diglyceride (MGDG) due to summer 03 exposures were found. Molar percentages and ratios of fatty acids did not change much in other lipids bur these changes in plastidie MGDG could be traced to a significant effect of summer O3 on the δ4 - 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 δ5 -isomers, are very different in shape to the δ5 -series and this may account, in part, for the extremely low winter temperatures from which Norway spruce needles may recover.
ABSTRACT
There are always significant pigment changes in Norway spruce [Picea abies (L.) Karst.] needles with time in different year classes, even through the winter, but no significant changes in current year needles occur either during summer exposure due to ozone (70 nl i-1 ) or in the winter following. Effects of summer ozone fumigation on pigment levels, however, are very evident in 1- (and 2-)yr-old needles. These include significant decreases of total amounts of chlorophyll a and b, violaxanthin, antheraxanthin, and lutein. The only increase in pigment of 1-yr-old needles in the summer caused by ozone is that of 5, 6-epoxy-lutein; consequently, the 5, 6-epoxy-lutein/lutein ratio rises. Although traces of 5, 6-epoxy-lutein also occur in the winter afterwards, they are not significant but significant decreases in levels of chlorophylls, vioiaxanthin, antheraxanthin, lutein and ß-carotene persist. The fall in chlorophyll a levels are greater than those of chlorophyll b so a significant fall in the chlorophyll a/b ratio also occurs. Similarly, the declines in amount of ß-carotene are not as great as those of chlorophyll a and therefore significant increases in the ratio of ß-carotene to chlorophyll a are observed. No time x treatment interactions occur after ozone fumigation of 1-yr-old needles has been stopped but time x ozone interactions are observed during fumigation in both chlorophyll a/b and violaxanthin/antheraxanthin ratios. Most pigment changes in 2-yr-old needles due to summer ozone exposure are complementary to those which occurred in 1-yr-old needles in response to ozone the summer before.
