© 1986 Heron Publishing—Victoria, Canada
Stomatal resistance, photosynthesis and water relations in mountain birch in the subarctic
Heikki Kauhanen
Department of Biology, University of Turku, 20500 Turku, Finland /
Summary
The role of water in regulating stomatal aperture and carbon assimilation of mountain birch (Betula pubescens Ehrh. ssp. tortuosa (Ledeb.) Nyman) was studied in the Swedish Subarctic. Stomata exhibited a clear response to changes in humidity and water
potential. High evaporative demand caused stomatal closure at midday. The diurnal curve of net photosynthesis, measured on
a warm day in early July, had two peaks, and photosynthetic rate was reduced by 25–30% at midday.
