Free radical scavengers and photosynthetic pigments in Pinus cembra L. needles as affected by ozone exposure

The goal of this study was the characterization of the antioxidative protec tion system of current and I-year-old needles of a cembran pine (Pinus cemb ra L.) and its possible responses to elevated concentrations of atmospheric O-3. Twigs of a mature cembran pine at the alpine timberline (1950 m a.s.l .) were exposed in climate-controlled twig chambers for 91 d to charcoal-fi ltered air (CF), ambient air O-3 concentration (A), and two-fold ambient ai r O-3 concentration (2A). Additionally, a chamberless control group (AA) wa s used to examine chamber effects. At the end of the fumigation period the contents of free radical scavengers and photosynthetic pigments were measur ed in the needles. Independent from O-3 exposure, total ascorbate and a-toc opherol contents were higher in I-year-old needles compared to the current flush while the opposite was found for glutathione. The amounts of pigments and antioxidants in P. cembra needles were comparable to those in other co nifers growing at high-elevation sites. The only hint toward O-3 induced ch anges in the composition of antioxidants was an increase in the glutathione redox state toward more oxidation in I-year-old needles upon exposure to A or AA conditions, but not upon 2A exposure. Chlorophyll and carotenoid con tents were not affected by O-3 neither in current- nor in previous-year nee dles. The de-epoxidation state of the xanthophyll cycle pigments, however, was significantly increased in I-year-old needles under A and AA compared t o the CF control, but not under 2A. Hence, Pinus cembra, which is well adap ted to the extreme environment of the timberline ecotone, exhibited only ma rginal biochemical changes in response to elevated O-3.