Apoplastic and total peroxidase activities in Scots pine needles at subarctic polluted sites

Abstract

A gradient survey was carried out in order to compare peroxidase activity in Scots pine (Pinus sylvestris) needles in relation to distance from the industrial centre of Monchegorsk, on the Kola Peninsula in north‐western Russia. Apoplastic and total peroxidase activity and sulphur (S), nickel (Ni) and copper (Cu) content in the needles of mature trees were measured on seven plots located between 10 and 110 km from the pollution source. Peroxidase activities in both current‐ and previous‐year needles increased towards the smelters and showed a positive correlation with needle S, Cu and Ni concentrations. Total peroxidase activities showed a more obvious relationship to the pollution gradient in winter than in autumn. The element contents in the current year needles averaged 1649 ppm (S), 128 ppm (Ni) and 118 ppm (Cu) close to the smelters, 1212 ppm (S), 37 ppm (Ni) and 67 ppm (Cu) at a distance of 40 km and 831 ppm (S), 7 ppm (Ni) and 1 ppm (Cu) at the most distant sampling plot.This study showed that both the apoplastic and total peroxidase activities responded to heavy metal and sulphur pollution up to 40 km from the smelters in winter, which indicated an increased oxidative stress in this area. The harsh climate conditions and the high pollution levels may have had additive effects. However, as peroxidases are considered a general indicator of stress, it is not possible to evaluate the extent to which single pollutants contribute to this enzyme activity.