Influence of altitude, sampling year and needle age class on stress-physiological reactions of spruce needles investigated on an Alpine altitude profile

The aim of the presented study was to characterize the physiological state of spruce needles from an alpine profile depending on altitude (970-1420 m above sea level) and needle age class (current year needles, one-year-old needles) during two consecutive years by investigating components of the antioxidative scavenging system (water extractable thiols, ascorbic acid, total peroxidase). The chlorophyll content was measured as a non-specific indicator of the general plant condition. With the exception of thiols the one-year-old needles always had higher needle contens of antioxidants and chlorophylls and the means of thiols and chlorophylls were significantly higher in the second sampling year. A more or less continous increase of antioxidants and a decrease of chlorophylls with increasing altitude was observed from the middle elevations (1140-1240 m a.s.l.) up to the highest site near the timberline (1420 m a.s.l.) and was interpreted as a response of the needles to increased oxidative stress due to the more uncomfortable environmental conditions at these elevations. However, high levels of antioxidants near the valley bottom (970-1050 m a.s.l.) also indicated an enhancement of the detoxification system and rather low chlorophyll levels (means of one-year-old needles <1100 mu g/g dw) probably reflected high environmental impact on the trees at these sites.