The slices were washed with deionized water and mounted on slides prior to their observation by fluorescence microscopy (OLYMPUS Provis AX 70 fluorescence microscope) or confocal laser scanning microscopy (TCS Leica SP Confocal

Laser Scanner Microscope, Leica, Heidelberg, Germany) at the SCSIE (UVEG, Valencia). Isolated photobionts of Ramalina farinacea The photobiont R. farinacea (Trebouxia sp.) was isolated following the protocol described by Gasulla et al. [28]. Basically, it involves homogenization of lichen thalli (from 15 mg to 2 g), a one-step centrifugation through Percoll (r), followed by washing with Tween 20 and sonication. Algae were grown in 3N Bold’s basal medium (BBM3N) containing 10 g casein and 20 g glucose per liter [29] with a 16:8 h light:dark photoperiod and at selleck inhibitor a temperature of 15°C. The medium was changed every 2 weeks and the concentration check details of algae set at 105 cells/ml. Physiology of photosynthesis

An axenic strain of the lichen photobiont Asterochloris erici (Ahmadjian) Skaloud et Peksa (SAG 32.85 = UTEX 911) was used for this study. Algae were grown on cellulose-acetate discs on agar BBM3N containing 10 g casein and 20 g glucose per liter [29, 30]. Cultures were maintained at 20°C under a 12 h photoperiod with 30 μmol m-2s-1 white-light illumination. After 21 days, the discs were removed from the culture medium and dried in a closed container with a saturated solution of ammonium nitrate (R.H. 62%), and maintained under culturing conditions. The samples remained in the dried state for 24 h, were then rehydrated with distilled water or 200 μM c-PTIO and returned to

culture conditions for 24 h. In vivo chlorophyll a fluorescence was measured with a modulated light fluorometer (PAM-2000, Walz, Effeltrich, Germany). The samples were kept in the dark for 30 min and the minimum (dark) fluorescence yield (Fo) measured after excitation of the algae with a weak measuring beam from a light-emitting diode. The maximum fluorescence yield (Fm) was determined with an 800 ms saturating pulse of white light (SP, 8000 μmol m-2 s-1). Variable fluorescence (Fv) was calculated as Fm-Fo, and the maximum quantum yield of photosystem II (PSII) Resminostat as Fv/Fm. The samples were allowed to re-adapt in the dark for 2 min, after which actinic light (AL, 200 μmol m-2 s-1, unless otherwise stated) was switched on, and SPs were applied at 1 min intervals to determine: (1) the maximum fluorescence yield during actinic illumination (F’m), (2) the level of modulated fluorescence during a brief (3 s) interruption of actinic illumination in the presence of 6 μmol m-2 s-1 far red (FR, 730 nm) light (F’o), and (3) steady-state chlorophyll a fluorescence yield after 11 pulses (Fs). Photochemical quenching (qP), and the quantum efficiency of PSII photochemistry (ФPSII) were estimated following the methods of Genty et al. [31] and Kramer et al. [32].