FTIR Nanospectroscopy Shows Molecular Structures of Plant Biominerals and Cell Walls

Plant tissues are complex composite structures of organic and inorganic components whose function relies on molecular heterogeneity at the nanometer scale. Scattering-type near field optical microscopy (s-SNOM) in the mid-infrared (IR) region is used here to collect IR nanospectra from plant samples of different preparations. We compared structures of chemically extracted silica bodies (phytoliths) to silicified and non-silicified cell walls prepared as flat block of epoxy embedded awns of wheat (Triticum turgidum), thin sections of native epidermis cells from sorghum (Sorghum bicolor) comprising silica phy-toliths, and isolated cells from awns of oats (Avena sterilis). The correlation of the scanning-probe IR images and the me-chanical phase image enables a combined probing of mechanical material properties together with the chemical composi-tion and structure of both the cell walls and the phytolith structures. The data reveal a structural heterogeneity of the differ-ent silica bodies in situ, as well as different composition and crystallinity of cell wall components. In conclusion, IR nano-spectroscopy is suggested as ideal tool for studies of native plant materials of varied origins and preparations, which could be applied to other inorganic-organic hybrid materials.