Evaluating the superoxide dismutase activity and chlorophyll fluorescence in Picea abies leaves growing at different altitudes

Superoxide dismutase (SOD) activity and parameters of chlorophyll fluorescence, the ratio of maximal to variable fluorescence (F-v/F-m), maximal fluorescence (F-m), and minimal fluorescence (F-0) were determined on Picea abies growing at different altitudes. The decreases of F-v/F-m and F-m, in comparison to samples from the lower stands (control), were found on trees from the highest stands. The decrease of fluorescence parameters was reversible, at least partly, after keeping the branches for some days in the laboratory. F-v/F-m measured in spring when trees were partially covered with snow revealed greater degree of photoinactivation in branches collected from above the snow in comparison to those from below the snow. In samples collected from above snow also slower recovery from stress was observed. Two main SOD isoforms were determined in needles of P. abies, and classified as CuZnSODs. The activity of both SOD isoforms was increasing with the altitude, thus indicating the highest level of oxidative stress at the timberline zone.