Description: The aim of the study was to determine the seasonal patterns of leaf transpiration (E) and stomatal conductance (gs) of young beech trees in relation to the air pollution in two forest sites with different hydrologic regimes - Vitinya and Petrohan. In Vitinya - with a less amount of rainfalls, a progressive decrease in E and gs from the beginning to the end of the growing season of 2009 was observed. A similar decrease in the two physiological parameters was found for Petrohan only in the summer. A significant non-linear correlation between gs in the sunny leaves and SO2 was found in Petrohan. At this site, gs in all leaves was related with NOx, while E was in a close correlation with the cumulative ozone exposure index AOT40

Remarks: Proceedings of the XI National Conference on Plant Physiology, 18-19 november 2009, Sofia, Bulgaria