ABSTRACT
Lipids were extracted from needles of Norway spruce plants of different provenances. The plants, seeds of which were originally collected from all over Europe, were grown at two sites in England at the same longitude but one 350 km north of the other. Significant correlations were observed between monogalactosyl diglyceride (MGDG) and digalactosyl diglyceride (DGDG) ratios on the one hand and, on the other, the lowest extreme winter temperature at the original site of seed collection (EWTS). In the case of lipid changes, however, environmental differences due to site were more important than the inherent genotypic characteristics of the planted trees while provenances with the lowest EWTS values had more MGDG than DGDG. This implies that existing winter hardiness under mild climatic conditions does not come from changes in this ratio although DGDG formation from MGDG is known to be an important feature of winter hardening in Norway spruce elsewhere in Europe. However, closer analysis of the fatty acids in lipids from provenances at individual sites did reveal significant correlations between those provenances with low EWTS values and certain molar amounts or ratios of fatty acids in DGDG, some of which could be traced to genotypic expression. These partly involved the unusual Δ5 desaturations which are mainly confined to the fatty acids of those conifers like Norway spruce that harden to very low temperatures.
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.
ABSTRACT
Atmospheric pollution by the oxides of nitrogen, NO and NO2 , can cause reductions in growth but rarely visible injury. This review considers their uptake into foliage, as well as their subsequent metabolism and physiology, and attempts to explain why these gases are often phytotoxic. The combined stresses of resisting cellular acidification, enhanced levels of nitrite (and ammonia), and the direct interference of the free radical ('N=O) with critical enzymes, reaction centres and regulatory mechanisms are thought to be the main reasons why oxides of nitrogen, especially NO, inhibit growth. If other air pollutants such as SO2 are also present with NO or NO2 then free radical-induced injury, similar to that caused by O3 alone, also occurs. CONTENTS Summary 395 I. Introduction 396 II. Uptake and cycling of oxides of nitrogen 396 III. Biochemical responses to NO and NO2 405 IV. Physiological responses to NO and NO2 410 V. Combinations of NO and NO2 with other pollutants 416 VI. Recapitulation and beyond 418 Acknowledgements 420 References 420.
