title: Parietin, a photoprotective secondary product of the lichen Xanthoria parietina.
abstract: Secondary lichen products can be extracted from air-dry thalli of Xanthoria parietina, Xanthoparmelia conspersa and Parmelina tiliacea with 100% acetone without affecting either short-or long-term viability. In Xanthoria parientina damage by acetone started to occur as water content reached the critical lower limit for photosystem II (PSII) activity. Extraction of the blue-light absorbing cortical pigment parietin increased the susceptibility of both air-dry and hydrated thalli to high light. Damage by high light levels caused a permanent reduction in Fv/Fm, quantum yield for photosynthetic O2production and photosynthetic capacity measured after a 2-day recovery period at low light levels (20 μmol photons m-2s-1). Parietin therefore protects the photosynthetic apparatus of Xanthoria parietina against damage by high light levels. Extraction of UV-absorbing pigments from Xanthoparmelia conspersa and Parmelina tiliacea did not increase photoinhibition after 24 h exposure to high light.
authors.affiliation: Department of Biology and Nature Conservation, Agricultural University of Norway, P.O. Box 5014, N-1432, Ås, Norway.
authors.forename: Knut A
authors.initials: KA
authors.lastname: Solhaug
authors.affiliation: Department of Biology and Nature Conservation, Agricultural University of Norway, P.O. Box 5014, N-1432, Ås, Norway.
authors.forename: Yngvar
authors.initials: Y
authors.lastname: Gauslaa
keywords: Acetone-rinsing; Chlorophyll fluorescence; Cortical pigments; Light screening; Photosynthesis