Blue skylight spectrum, Chlorophyll fluorescence decrease ratio RFd, Fluorometer module, Induction kinetics, Kautsky effect, Light adaptation, Net photosynthetic CO2 fixation, Spectral irradiance of half-shade and full shade

The chlorophyll (Chl) fluorescence induction kinetics, net photosynthetic CO2 fixation rates P N, and composition of photosynthetic pigments of differently light exposed leaves of several trees were comparatively mea- sured to determine the differences in photosynthetic activity and pigment adaptation of leaves. The functional mea- surements were carried out with sun, half-shade and shade leaves of seven different trees species. These were: Acer platanoides L., Ginkgo biloba L., Fagus sylvatica L., Platanus x acerifolia Willd., Populus nigra L., Quercus robur L., Tilia cordata Mill. In three cases (beech, ginkgo, and oak), we compared the Chl fluorescence kinetics and photosynthetic rates of blue-shade leaves of the north tree crown receiving only blue sky light but no direct sunlight with that of sun leaves.