摘要：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.
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