Effects of UV-B radiation and water stress on chlorophyll fluorescence parameters and activity of xanthophyll cycle in leaves of sessile oak (Quercus petraea) seedlings

Abstract

In the present study we investigated the photosynthetic responses of sessile oak seedlings to UV-B radiation and water stress in growth chamber experiment. Seedlings of sessile oak showed sensitivity to enhanced UV-B radiation which appeared in decreases of maximum photochemical efficiency (Fv/Fm) and actual photochemical efficiency of PSII ($F/Fm’). UV-B radiation and water stress induced 150 and 170 % increase of non-photochemical fluorescence quenching (NPQ) and threefold and fourfold elevation of activity of xanthophyll cycle as compared to the control, respectively. Seedlings exposed simultaneously to UV-B and water stress induced larger decrease of Fv/Fm, $F/Fm’ and RFD than those exposed separately to enhanced UV-B or water withdrawal as compared to control plants. Both UV-B radiation and water stress increased non-photochemical quenching with a parallel enhancement of zeaxanthin formation.