Analytical and Bioanalytical Chemistry

, Volume 389, Issue 4, pp 1249–1257

Structural and analytical studies of silica accumulations in Equisetum hyemale

  • Lanny Sapei
  • Notburga Gierlinger
  • Jürgen Hartmann
  • Robert Nöske
  • Peter Strauch
  • Oskar Paris
Original Paper

DOI: 10.1007/s00216-007-1522-6

Cite this article as:
Sapei, L., Gierlinger, N., Hartmann, J. et al. Anal Bioanal Chem (2007) 389: 1249. doi:10.1007/s00216-007-1522-6

Abstract

Horsetail (Equisetum spp.) is known as one of the strongest accumulators of silicon among higher terrestrial plants. We use the combination of position-resolved analytical techniques, namely microtomography, energy-dispersive X-Ray elemental mapping, Raman microscopy, as well as small-angle and wide-angle scattering of X-rays, to study the type, distribution and nanostructure of silica in the internodes of Equisetum hyemale. The predominant silicification pattern is a thin continuous layer on the entire outer epidermis with the highest density in particular knob regions of the long epidermal cells. The knob tips contain up to 33 wt% silicon in the form of pure hydrated amorphous silica, while the silica content is lower in the inner part of the knobs and on the continuous layer. In contrast to the knob tips, the silica in these regions lacks silanol groups and is proposed to be in close association with polysaccharides. No mentionable amount of crystalline silica is detected by wide-angle X-ray scattering. The small-angle X-ray scattering data are consistent with the presence of colloidal, sheet-like silica agglomerates with a thickness of about 2 nm. From these results we conclude that there are at least two distinct forms of silica in E. hyemale which may have different functions. The close association of silica with cell wall polymers suggests that they may act as a polymeric template that controls the shape and size of the colloidal silica particles similar to many other biominerals and mineralised tissues. We propose that owing to its specific distribution in E. hyemale, a protective role and possibly also an important biomechanical role are among the most likely functions of silica in these plants.

https://static-content.springer.com/image/art%3A10.1007%2Fs00216-007-1522-6/MediaObjects/216_2007_1522_Figa_HTML.gif
Figure

3D rendering of X-ray microtomography data from a dry Equisetum hyemale stalk. The red colour indicates high X-ray absorption values due to local silica accumulations

Keywords

Equisetum hyemaleSilicaRaman microscopyMicrotomographySmall-angle X-ray scatteringWide-angle X-ray scattering

Copyright information

© Springer-Verlag 2007

Authors and Affiliations

  • Lanny Sapei
    • 1
  • Notburga Gierlinger
    • 1
  • Jürgen Hartmann
    • 2
  • Robert Nöske
    • 3
  • Peter Strauch
    • 3
  • Oskar Paris
    • 1
  1. 1.Department of BiomaterialsMax Planck Institute of Colloids and InterfacesPotsdam-GolmGermany
  2. 2.Department of ColloidsMax Planck Institute of Colloids and InterfacesPotsdam-GolmGermany
  3. 3.Department of ChemistryPotsdam UniversityPotsdam-GolmGermany