TY - JOUR N2 - Diurnal measurements of photosynthetic pr ocesses, effective quantum yield of photosystem II ( F PSII ), photosynthetic electron transport rate (ETR) were done in three domi− nant species of Arctic tundra ( Silene acaulis , Dryas octopetala , Salix polaris ) in Petunia− bukta, Spitsbergen. Daily courses of net photosynthesis (P N ) were calculated from chloro− phyll fluorescence data and daily photosynthesi s evaluated. The short−term field measure− ments were carried out in summer 2009, and 2010. Fluorometric parameters ( F PSII and ETR) were measured each 5 minutes as well as microc limate characteristics of the site for 10 (2009) and 8 days (2010), respectively. In all species photosynthetic ETR was well related to incident photosynthetically active radiation a nd leaf temperature. In general, D. octopetala exhibited slightly lower ETR than the other two speci es. Estimated maximu m photosynthetic rate (P Nmax ) reached 17.6, 21.4, and 22.9 μmol CO 2 m −2 s −1 for S. polaris , S. acaulis ,and D. octopetala , respectively. Daily photosynthesis reach ed comparable values in all species, D. otopetala , however, exhibited slightly lower values than the other two species both for overcast and fully sunny days (3.9 and 13.4 mmol CO 2 m −2 d −1 , respectively). The range of daily photosynthesis for S. polaris and S. acaulis studied, reached the ranges of 4.6–6.9 and 14.6–15.2 mmol CO 2 m −2 d −1 for overcast and fully sunny day, respectively. L1 - http://journals.pan.pl/Content/99537/PDF/v10183-012-0018-z.pdf L2 - http://journals.pan.pl/Content/99537 PY - 2012 IS - No 4 EP - 462 DO - 10.2478/v10183−012−0018−z KW - Arctic KW - Svalbard KW - vascular plants KW - plant ecophysiology KW - net photosynthesis KW - chlorophyll fluorescence A1 - Barták, Miloš A1 - Váczi Peter A1 - Hájek, Josef PB - Polish Academy of Sciences PB - Committee on Polar Research DA - 2012 T1 - Photosynthetic activity in three vascular species of Spitsbergen vegetation during summer season in response to microclimate SP - 443 UR - http://journals.pan.pl/dlibra/publication/edition/99537 T2 - Polish Polar Research ER -