| Summary: | Maximum values of chlorophyll (Chl) (a + b) content, potentíal (Pp) and net (Pu) photosynthetíc rate in the populatíon of 25 species growing in the tundra of Wrangel Island are presented. Field measurements of response of Pp and P^ to irradiance were doně. Maximum Chl content in arctic plants was typically low [O.S-2.9 g kg'i(f.m.)] and rather close to tíie range characterizing extreme biomes: i.e. deserts and high mountains. By contrast, the sum of carotenoids (Car) was hi^ [1.1-2.3 g kg-i(d.m.)]. In most tundra plants the ratío Chl/Car varied firom 4 to 5. Lower values of Chl/Car were observed only in the high mountain plants of the Paniirs. The peculiarity of pigment apparatus organization in arctic species was expressed in low values of the ratío of pigment-protein complexes LHC/CPl + CP2 dut was mostly close to 1 or lower, as well as in the smáli size of photosynthetíc unit which was 100-200 molecules. Irradiance response of photosynthesis, pigments and structure characteristics indicated features usually considered typical bodi of sun and shade tolerant plants. Their high ability to adapt both to low and high irradiance at low temperature is a substantíal guarantee for 24-h photosyndiesis during polar day.
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