Role of antioxidant enzymes in the seasonal adaptation of Picea omorika (Pančić) Purkyne

Abstract

We studied seasonal variation in the achv1ty and isoenzyme pattern of peroxidase, catalase, catechol oxidase and superoxid-dismutase in the needles of Picea omorika (Pancic) Purkyne trees. The samples were collected from the natural habitat of the species, Mt. Tara. This endemic coniferous species is exposed to subfreezing temperatures that range from -10 to -30°C during the autumn/winter and high temperatures exceeding 30°C during the summer. Characteristic EPR signal of free or weakly bound Mn2+ was used as an indicator of oxidative status of needles, since cold-related oxidative damage leads to Mn2+ release from photosystem IL Seasonal changes were found to affect enzymatic activities and isoenzyme profiles. Several isofonns of peroxidase, catechol oxidase and superoxide dismutase, as well as two catalase isoenzymes were detected. The number of peroxidase isoenzymes was greatest during the vegetative season. The results obtained show that there are two gro ups of antioxidant enzymes in P. omorika needles that change levels of activities in the spring/summer and autumn/winter seasons. Catalase and catechol oxidase peaked in summer and spring, respectively. During the autumn/winter season, however, both total SOD and Mn-SOD showed maximum activity. It was observed that prooxidative conditions developed in the autumn, at the beginning of cold season, which corresponded to significant increase of MnSOD activity. This suggests a complementary action of these enzymes in reaction to external changes.