Biochemical traits of lichens differing in relative desiccation tolerance.

• Oxidative stress arises when desiccation restricts photosynthesis and light energy is transferred from photo-excited pigments onto ground state oxygen. We tested whether a highly desiccation tolerant lichen, Pseudevernia furfuracea, displays better protection against oxidative stress than more sensitive species, Lobaria pulmonaria and Peltigera polydactyla. • We rehydrated lichens after desiccation periods of 2, 7 and 9 weeks and assessed their viability by measuring CO2 exchange using IRGA. During desiccation and rehydration, photosynthetic pigments and the antioxidant α-tocopherol were analysed by HPLC, and peroxidases by spectrophotometry. •  Pseudevernia furfuracea contained considerably lower chlorophyll, α-tocopherol and β-carotene concentrations and peroxidase activity than the two other lichens. However, it recovered photosynthesis rapidly, even after remaining in the desiccated state for 2 months while there was a significant delay in the onset of photosynthesis in L. pulmonaria and P. polydactyla. • We conclude that high antioxidant concentrations do not necessarily indicate better adaptation to desiccation. Rather, the ability to rapidly re-establish the species-specific normal antioxidant concentrations during rehydration, even after longer desiccation times, is a characteristic of well-adapted species.