Microscopic and NMR analysis of the external coat from seeds of Magonia pubescens.

•  The chemical composition and structure of the layers of the external coat and the three-dimensional organization of the gel during the swelling process are reported here for seeds of Magonia pubescens. •  Histochemical-light and scanning electron microscopy (SEM) were used in conjunction with CP-MAS (cross polarization - magic angle spinning: solid state) C NMR spectroscopy to analyse the seed coat layers. •  M. pubescens seeds extrude a gel from the second of five regions of the external seed coat when immersed in water. This gel, visualized by SEM, had an extruded cylindrical, laminated structure. Staining revealed two anionic components in the cells of the second layer; the cytoplasm showed the presence of carbohydrates containing vicinal hydroxyl groups and at least some of these carbohydrates were acidic polysaccharides. Part of the β-linked glucan present in this layer was cellulosic material. Phenolic compounds were not detected in the second layer, but existed in other layers. Lignin and/or tannins were shown in the cell walls of the three innermost layers by CP-MAS C NMR spectroscopy. •  The solid-state NMR technique had the advantage of being more sensitive and quantitative compared with light microscropy and might prove to be a useful tool in investigating cell components.