Wax composition on emerged and submerged helophyte stem sections varies more in Schoenoplectus acutus than in Eleocharis palustris

Helophytes stems emerge from shallow water, facing strongly contrasting environmental conditions over a short distance. Does their outermost barrier, the cuticle wax, vary within the same organ under these conditions? To explore this, we analyzed the cuticular wax composition in two sedges, Schoenoplectus acutus (hardstem bulrush) and Eleocharis palustris (common spikerush). Paired stem wax samples from below and above the waterline were analyzed by gas chromatography–mass spectrometry (GC–MS) for quantification and identification. In S. acutus, primary alcohols dominated below the waterline while decarbonylation-pathway products and alkylresorcinols were more abundant above the waterline. In E. palustris, wax quantity and major compound class composition were similar above and below the waterline. Waxes from both sedge species showed higher average chain lengths in the wax on the submerged portions of the stems. These findings indicate plants exhibit contrasting, spatially differentiated wax compositions between stem sections exposed to submerged versus emerged conditions.