THE INFLUENCE OF OZONE, ACID MIST AND SOIL NUTRIENT STATUS ON NORWAY SPRUCE [PICEA-ABIES (L) KARST] .2. PHOTOSYNTHESIS, DARK RESPIRATION AND SOLUBLE CARBOHYDRATES OF TREES DURING LATE AUTUMN

Three‐year old Norway spruce [Picea abies (L.) Karst.] trees of clonal stock originating from medium altitude in southern Germany were transplanted in May 1986 into two acid brown‐earth soils which differed particularly in the amounts of exchangeable Ca2+ and Mg2+. During the summers of 1987 and 1988 trees were exposed in large‐scale fumigation chambers (solardomes) to ozone at 200 or 40 (control) μg m−3 Acid (pH 3˙6) or control mist (pH 5˙5) solution was applied daily to trees in each half of the solardomes. In late autumn (1988) the light response of CO2 exchange, and the chlorophyll and soluble carbohydrate contents of needles were determined. Ozone and/or acid mist treatment had only minor (< 10%) effects on the light‐saturated rate of photosynthesis which were not statistically significant in plants from either soil. Needles from trees raised on the richer soil and exposed to a combination of ozone and acid mist showed a significant increase in the apparent quantum yield of photosynthesis which was associated with an increase in chlorophyll content. Ozone (alone) stimulated the rate of dark respiration by 40 and 58 % for trees grown in richer and poorer soils, respectively, and this was associated with a decrease in ethanol‐soluble carbohydrate content of needles. Where significant interactions between ozone and acid mist were found, they were generally antagonistic. The reduction in the ethanol‐soluble carbohydrates would be expected to reduce frost hardiness, and may contribute to the increased sensitivity of ozone‐treated needles to freezing, which has been reported in previous studies. Copyright © 1990, Wiley Blackwell. All rights reserved