Effect of ambient air pollutants on nitrogen metabolism, antioxidants and ð 13C-values in needles of Norway Spruce as compared to other environmental factors

1997

S. 175-200

6 Abb., zahlr. Lit. Ang.

Unselbständiges Werk

200104691

Spruce trees (Picea abies) kept in open-top chambers with charcoal-filtered and non-filtered air (sample size n=4) at the Edelmannshof site from 1987-1992 were studied to evaluate the impact of ambient air pollution on needle metabolism. Seasonal and diurnal variations in N-metabolism (soluble amino acids, protein, glutamine synthetase and glutamate dehydrogenase) and antioxidants (ascorbate, glutathione and different peroxidases) were investigated in the young needles till the end of the second vegetation period. Additionally, ð 13C-values were measured in needle samples from the Edelmannshof site and in needles of Pinus taeda exposed to different ozone concentrations in the Duke Forest, NC. There was an increase of the ð 13C-values in loblolly pine needles if ozone level increased. However, at the Edelmannshof site only a great variation between the trees could be found but no treatment effect. Based on all the data from 1988-1992 the typical seasonal curves of the different physiological parameters of the three groups (charcoal-filtered, non-filtered, ambient) were determined. There was no definite difference between the trees kept in chambers with charcoal-filtered and non-filtered air, but significant chamber effects on ascorbate and glutathione content. Moreover, great variations were found between the trees and the four years of exposure. Therefore physiological data were compared with the available values of the respective environmental conditions from 1989 till 1991 by regression analysis. It was found that components of the nitrogen metabolism and ascorbate content depended on the water supply and increased under water stress conditions. For soluble protein content r2 amounted to 0.62 indicating that water supply is a main factor influencing needle metabolism. It is concluded that the trees at the Edelmannshof site are more affected by other environmental factors than by ambient air pollution.