Photoinhibition of primary photosynthetic processes in hydrated Polytrichum commune: Analysis of non-photochemical quenching affecting species resistance

A moss from the alpine environment of the Jeseníky mountains, Polytrichum commune, was studied under lab-induced light stress to analyse photoinhibition (PI) stress response; three PI doses were used: PAR 1500 µmol m-2 s-1 for 60 min., 1200 µmol m-2 s-1 for 60 min. and 1200 µmol m-2 s-1 for 30 min.; in the last one the added component of slight desiccation stress was added. Chlorophyll fluorescence parameters were plotted as time series, immediately before and after the PI treatments, then every 20 minutes for three hours (recovery period). FV/FM, ΦPSII and NPQ parameters and quenching components were analysed. Decreasing courses and final values of FV/FM and ΦPSII parameters along with increased values of NPQ clearly indicated PI stress response, although not very severe. Quenching parameters analysis showed a dominant role played by xanthophyll pigments along with changes in PS II in the non-photochemical energy quenching. Dehydration contributed additional value to NPQ. All these factors are consistent with the adaptation of the species to harsh conditions of alpine environments.