Tilted cellulose arrangement as a novel mechanism for hygroscopic coiling in the stork's bill awn

Yael Abraham, Carmen Tamburu, Eugenia Klein, John W.C. Dunlop, Peter Fratzl, Uri Raviv, Rivka Elbaum*

*Corresponding author for this work

Research output: Contribution to journalReview articlepeer-review

88 Scopus citations


The sessile nature of plants demands the development of seed-dispersal mechanisms to establish new growing loci. Dispersal strategies of many species involve drying of the dispersal unit, which induces directed contraction and movement based on changing environmental humidity. The majority of researched hygroscopic dispersal mechanisms are based on a bilayered structure. Here, we investigate the motility of the stork's bill (Erodium) seeds that relies on the tightening and loosening of a helical awn to propel itself across the surface into a safe germination place. We show that this movement is based on a specialized single layer consisting of a mechanically uniform tissue. A cell wall structure with cellulose microfibrils arranged in an unusually tilted helix causes each cell to spiral. These cells generate a macroscopic coil by spiralling collectively. A simple model made from a thread embedded in an isotropic foam matrix shows that this cellulose arrangement is indeed sufficient to induce the spiralling of the cells.

Original languageAmerican English
Pages (from-to)640-647
Number of pages8
JournalJournal of the Royal Society Interface
Issue number69
StatePublished - 7 Apr 2012


  • Cellulose
  • Coiling
  • Erodium
  • Hygroscopic movement
  • Microfibril angle
  • Small-angle X-ray scattering


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