Glutathione concentrations in C. aculeata and D. muscorum samples representing control and experimental groups (square = mean, box = SE, whisker = 95% confidence interval, for C. aculeata n = 8, for D. muscorum n = 6): a GSH concentration, b GSSG concentration, and c total glutathione concentration. The different letters above the bars indicate significant differences (p < 0.05). Lowercase letters indicate significant interaction, and capital letters indicate the significant effect of lichen species. The asterisk indicates a significant effect of the experimental group. For details see Suppl. material 1: table S1.