THE EFFECTS OF ENHANCED OZONE AND ENHANCED CARBON-DIOXIDE CONCENTRATIONS ON BIOMASS, PIGMENTS AND ANTIOXIDATIVE ENZYMES IN SPRUCE NEEDLES (PICEA-ABIES L)

During one growing period, 5-year-old spruce trees (Picea abies L., Ka rst.) were exposed in environmental chambers to elevated concentration s of carbon dioxide (750 cm3 m-3) and ozone (0.08 cm3 m-3) as single v ariables or in combination. Control concentrations of the gases were 3 50 cm 3 m-3 CO2 and 0.02 cm3 m-3 ozone. To investigate whether an elev ated CO2 concentration can prevent adverse ozone effects by reducing o xidative stress, the activities of the protective enzymes superoxide d ismutase, catalase and peroxidase were determined. Furthermore, shoot biomass, pigment and protein contents of two needle age classes were i nvestigated. Ozone caused pigment reduction and visible injury in the previous year's needles and growth reduction in the current year's sho ots. In the presence of elevated concentrations of ozone and CO2, grow th reduction in the current year's shoots was prevented, but emergence of visible damage in the previous year's needles was only delayed and pigment reduction was still found. Elevated concentrations of ozone o r CO2 as single variables caused a significant reduction in the activi ties of superoxide dismutase and catalase in the current year's needle s. Minimum activities of superoxide dismutase and catalase and decreas ed peroxidase activities were found in both needle age classes from sp ruce trees grown at enhanced concentrations of both CO2 and ozone. The se results suggest a reduced tolerance to oxidative stress in spruce t rees under conditions of elevated concentrations of both CO2 and ozone .