Sulphate and antioxidants in needles of Scots pine (Pinus sylvestris L.) from three SO2-polluted field sites in Eastern Germany
Needles from young and mature Scots pine trees (Pinus sylvestris) were collected at three field sites in eastern Germany, i.e. Menz, Taura, and Gossa, which differed in SO2 pollution. Current and previous year's needles from the polluted sites Taura and Gossa (yearly mean of SO2: 26 ppb) contained approximately 100-1 20 my mol sulphate g(-1) d. wt, whereas needles from the unpolluted site, Menz (yearly mean of SO2: 3 ppb) contained 30-65 my mol sulphate g(-1) d. wt. The apoplastic sulphate content was in the order of 0.3-1 per cent of total sulphate and corresponded to concentrations of 0.6-1.2 mm in needles from Menz and to 1.5-2 mm in needles from Gossa. In needles from the polluted sites the contents of glutathione, cysteine, -gamma-glutamylcysteine, and soluble protein were higher than in needles from Menz. Despite the clear increases in sulphur-containing compounds, pigment content and activities of superoxide dismutase, total peroxidase and apoplastic peroxidase (on the basis of d. wt) were not significantly different. When enzymatic activities were related to protein, lowest activities were found in needles from the site with the highest SO2-pollution. The results show that it is not possible to use the activities of peroxidases or superoxide dismutases as biomarkers for SO2-mediated stress in pine needles. It remains open whether the needles from the polluted sites suffered from greater oxidative stress than the needles from the less polluted site.