We assessed physiological characteristics (chlorophyll a fluorescence, photosynthetic pigments) of shade leaves of the beech (Fagus sylvatica L.) in (measured 1, 2, 3, 7 and 14 days before the leaf sampling). The study was performed in two locations under different pollution load. The leaf characteristics were observed on 15 year old trees from the understorey. We identified a significant negative influence of the temperature difference related to the long term average (25 years) on the basic fluorescence (F 0) and a positive influence of deviation of maximum temperatures from the long term average on the ratio of the variable to maximum fluorescence (Fv/Fm). These trends were observed for short time periods (1-3 days) and they were mainly true for parameters measured on upper (adaxial) side of assimilatory organs of trees at both localities. In the photosynthetic pigments it is significant influence of the deviation of maximum temperatures measured one day before the leaf sampling on the pigment content values (mg.dm-2) at both localities.