Environ Exp Biol (2018) 16: 117–127

Different plant species accumulate various concentration of Na⁺ in a sea-affected coastal wetland during a vegetation season

Abstract

The aim of the present study was to determine if plant species coexisting in highly heterogeneous conditions of coastal wetland display different strategies in respect to accumulation of Na⁺ in their tissues. A 50-m-long transect was established in a sea-affected wetland on the coast of the Riga Bay of the Baltic Sea in the territory of Mērsrags, Latvia. Several plant species both in a wetland part (Rumex hydrolapathum Huds, Bolboschoenus maritimus (L.) Palla, Scirpus tabernaemontani C. C. Gmel., Juncus compressus Jacq.) and drier part [Trifolium pratense L., Taraxacum officinale (L.) Weber ex F. H. Wigg. and Festuca arundinacea Schreb.] of the transect were sampled four times during the vegetation season. Soil electrical conductivity as well as Na⁺ and K⁺ concentration in soil solution were monitored along the transect. Soil electrical conductivity measured in field was highly fluctuating both on temporal and spatial scales, and concentration of Na⁺ in soil solution showed high temporal variability. Na⁺ concentration in leaf extracts showed a species-specific pattern with pronounced changes along the transect and during a vegetation season. Leaf Na⁺ concentration showed only species-specific weak to moderate correlation with Na⁺ concentration in soil solution indicating that other factors determined rate of Na⁺ accumulation in leaves. Leaf K⁺ concentration had only weak positive or even negative correlation with K⁺ concentration in soil solution, with exception of J. compressus and T. pratense, which had a moderately tight relationship. Leaf K⁺/Na⁺ concentration ratio was extremely variable. The highest values were evident in plants (T. pratense, T. officinale and F. arundinacea) from the drier part of the transect, especially, at low Na⁺ concentration in soil solution. In general, a positive correlation between K⁺/Na⁺ ratio and Na⁺ concentration in soil solution was characteristic for all plant species and it was moderate to high. For R. hydrolapathum, Na⁺ was excluded both from roots and flowers, and preferently accumulated in the oldest leaves and their petioles. R. hydrolapathum emerged as a potential Na⁺ accumulator species, as leaf Na⁺ concentration of plants growing in a sea-affected wetland was constantly higher than that of other adjacent species. These characteristics indicate potential of R. hydrolapathum in metal accumulation and as useful model species for phytoremediation studies.