ECOLOGICAL FEATURES ОF INFLUENCE ОF STOMATAL CONDUCTANCE ОN PHOTOSYNTHESIS IN A SCOTS PINE

Investigations of stomatal regulation of photosynthesis in Scots pine (Pinus sylvestris L.) in different ecological conditions are presented in this paper. Stomatal and mesophyll conductance to CO2 were calculated using measurements of photosynthesis, transpiration and environmental variables during the growing season in South Karelia. Correlation of photosynthesis with stomatal conductance was 60–80 %. Effects of other external and internal factors were less strong. Stomatal conductance mostly depended on the water pressure deficit in air (correlation of 40–60 %). The close correlation was found between stomatal conductance and mesophyll conductance (up to 75 %). During the period of intensive apical and radial growth in conditions of high air temperature, despite of considerable decrease of stomatal conductance, photosynthesis remained on a high level due to enhancement of exchange processes that was expressed in increasing of mesophyll conductance