WATER STATUS, PHOTOSYNTHETIC PIGMENTS, C/N RATIOS AND RESPIRATION RATES OF SITKA SPRUCE SEEDLING EXPOSED TO 70-PPBV OZONE FOR A SUMMER

Three-year old seedlings of Picea sitchensis (Bong.) Carr. were exposed in large-scale chambers (solardomes) to 70 ppbv O-3 for an entire summer, 7 hr day(-1), under approximately ambient conditions. No macro- or microscopic injury, no fluorescence differences and no growth rate effects were found in the fumigated spruce. However, fumigated seedlings showed significantly lowered water potentials, chlorophyll concentrations, nitrogen and sulfur contents, and respiration rates. The old needles had higher cyanide-resistant respiration. These results were consistent with symptoms of forest decline affecting high-altitude forest and showed the presence of physiological changes even though there were no visible symptoms.