Zosterin, an apiose-rich pectic polysaccharide, which is found in the sea grass Zostera marina is typical of similar structures occurring in higher plants. The structure consists of an α-1,4-D-galactopyranosyluronan backbone substituted by 1,2-linked apiofuranose oligosaccharides and single apiose residues. The average molecular mass of the polysaccharide has been shown to be about 4100 Da with a low polydispersity.