PHYSIOLOGY OF YOUNG NORWAY SPRUCE

In the Hohenheim experiment young spruce (Picea abies L. Karst.) were exposed to low levels of SO2 and/or O3 and acid precipitation. At the end of a five-year experimental period (1983-88) the following physiological parameters were examined: water soluble thiols, ascorbic acid, glutathione-reductase activity and pigment content. Exposure to SO2, leads to an increase in thiol content, to a slight decrease of ascorbic acid and to a pronounced decrease of pigments. O3 exposure increases the content of ascorbic acid and decreases the thiols and the glutathione-reductase activity with no change in the pigment content. The combined exposure to SO2, and O3 results in the most distinct deviations compared to the control chamber response. These needles show the highest increase of ascorbic acid and thiols, the dry weight is decreased as is the glutathione-reductase activity and the pigment content is reduced. Consequences of these physiological alterations for the plant's health are discussed.