Bedeutung der Glutathionreduktase für das antioxidative System der Eichen - Zusatzmaterial

The objective of the current study was to render insights into the contribution of glutathione reductase to the antioxidative system of oak trees. For this purpose, ten old-growth oak tree stands were analysed in two consecutive vegetation periods in Southwestern Germany (cf. Fig. 1, Tab. 1, 2). The investigations were complemented by site exchange, common garden and climate chamber experiments. In all investigations, leaves were analysed for carbon discrimination (d13C, stomatal conductance), relative water content (water status), hydrogen peroxide content (oxidative load), glutathione reductase activity (GR, regeneration of GSSG in the Foyer-Halliwell-Asada-cycle or suppression of lipid peroxidation), and malone dialdyhyde content (MDA, biomembrane damage). In young oak trees, GR activity was down-regulated, when grown under water limiting conditions (cf. Fig. 2; Tab. 3). This response was not observed in old-growth trees (cf. Tab. 3). There was no impact of the water status or oxidative load on GR activity. Apparently, GR activity is not triggered by abiotic stress and does not contribute to its control. However, GR was constantly and significantly governed by membrane desintegration both in young and old-growth oak trees as determined by MDA accumulation (cf Fig. 3; Tab. 4). Therefore, we conclude that GR activity in oak trees is not determined by the antioxidative system of the Foyer-Halliwell-Asada-cycle, but rather by biomambrane damage and the suppression and detoxification of lipid peroxidation.