FTIR Nanospectroscopy Shows Molecular Structures of Plant Biominerals and Cell Walls

V. M. R. Zancajo, T. Lindtner, M. Eisele, A. J. Huber, R. Elbaum and J. Kneipp

Anal. Chem. , Just Accepted (2020)
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.