Glutathione status and glutathione reductase activity in spruce needles of healthy and damaged trees at two mountain sites

Levels of glutathione, in both reduced and oxidized form, and glutathione reductase activity were monitored in needles of healthy and damaged spruce trees (Picea abies (L.) Karst.) during the course of four vegetation periods at two natural sites. The glutathione content and glutathione reductase activity showed a pronounced annual rhythm in undamaged trees, whereas damaged spruce trees deviated significantly from this course. In comparison with undamaged trees, damaged trees showed markedly increased levels of glutathione during the test period of 1989-1991. However, glutathione reductase activity differed in damaged and undamaged trees, only in 1989-1990. The ratio of reduced to oxidized glutathione (GSH/GSSG ratio) was slightly higher in damaged trees, and the highest levels were found during the winter months. In the case of damaged trees, a correlation between GSH/GSSG ratio and current ozone levels at the sites could be clearly established. The present results indicate that damaged trees suffer from increased oxidative stress, especially in the period from June to October.