Env Exp Biol (2012) 10: 89–97

Protection of photosynthesis in coastal salt marsh plants Aster tripolium and Hydrocotyle vulgaris in conditions of increased soil salinity

Abstract

The aim of the present study was to investigate if plants native to habitats with fluctuating soil salinity levels induce a higher level of photosynthesis protection in conditions of elevated salinity. Two plant species from a coastal salt marsh were used in the experiments – Aster tripolium and Hydrocotyle vulgaris. Changes in photosystem II photochemistry and protection under the effect of NaCl at different light intensities were characterized by chlorophyll a fluorescence and ascorbate peroxidase activity. NaCl-treated A. tripolium plants grown at moderate light tended to have higher maximum quantum use efficiency of photosystem II (Fv/Fm) over the control level. Relative electron transport rate (ETR) decreased in NaCl-treated plants. In contrast, thermal dissipation of excess energy measured as non-photochemical quenching (NPQ) increased. Treatment with 25 mM NaCl led to relatively small changes in Fv/Fm in H. vulgaris plants at all light intensities. At 100 mM NaCl a pronounced decrease of Fv/Fm was evident, which was more severe at moderate and high light. NaCl significantly inhibited ETR at both low and moderate light. However the decrease of ETR was only temporal. Similary, the treatment caused an increase of NPQ. Concentration-dependent increase of ascorbate peroxidase activity was found in leaves of A. tripolium treated with NaCl. In contrast, ascorbate peroxidase activity decreased in leaves of H. vulgaris. The data are discussed in respect to different strategies of adaptation of salt marsh plants to high soil NaCl.