Long-term manipulated warming experiments using the open top chamber (OTC) approach tend to mimick the future climate and predict the changes in photosynthesis and production of vegetation under globally changed climate. In Antarctica, several longterm experiments are carried out recently. Here we report to the lichens grown in OTCs installed at the Fildes Peninsula (King George Island). The field study compares primary photochemical processes of photosynthesis in Antarctic lichen Placopsis antarctica grown for one year in OTC and compared to outside plot (control). We measured effective quantum yield of photosystem II (ΦPSII) of green algae part of thallus in 10 min. interval for 12 days. We examined the responses of diurnal ΦPSII to PAR in relation to environmental factors through continuous 12-d-long monitoring of chlorophyll fluorescence parameters ΦPSII in particular. Daily courses of ΦPSII and photosynthetic electron transport rate (ETR) to photosynthetically active radiation (PAR) and hydration state of thallus have been assumed to reflect changes in physiological status of P. antarctica in changing Antarctic environment. The data indicate that OTC microenvironment may lead to partial limitation of photosynthetic processes in P. antarctica during austral summer season. The limitation is caused by accelerated dehydration of thallus in OTC compared to the outside generally colder control plot, and thus shortened physiologically active period of lichens in OTC.