Seasonality of glutathione dynamics in Scots pine and bilberry

Seasonal changes in the glutathione status of Scots pine (Pinus sylvestris L.) needles and bilberry (Vaccinium myrtillus L.) stems and leaves were inv estigated during 1995 and 1997-1998, respectively. The glutathione concentr ation, the proportion of reduced glutathione (GSH%) and glutathione reducta se (GR) activity were measured at monthly intervals throughout one year. Th e glutathione concentration and GSH% in current year's Scots pine needles w ere highest during late summer, but decreased during autumn. It is suggeste d that exchange reactions between free and protein-bound glutathione may be involved in this reduction. Both metabolites decreased towards summer in t he previous year's needles. GR activity exhibited the lowest values in summ er and the highest values in winter in both needle generations. In bilberry stems, glutathione peaked during midwinter, while GSH% remained high and r elatively constant throughout the year. GR activity was highest in August, after which it gradually declined. In bilberry leaves, the total glutathion e concentration was high in early summer. This peak was followed by a sharp decrease during midsummer. CR activity in the leaves was very low, but sho wed a clear increase towards autumn. Obviously, glutathione metabolism show ed considerable seasonal variation in Scots pine needles and in bilberry le aves and stems, but the pattern of variation differed between the studied s pecies and organs.