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Science 11 May 2007:
Vol. 316. no. 5826, pp. 884 - 886
DOI: 10.1126/science.1140097
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Reports

The Role of Wheat Awns in the Seed Dispersal Unit

Rivka Elbaum,1* Liron Zaltzman,1,2 Ingo Burgert,1 Peter Fratzl1*

The dispersal unit of wild wheat bears two pronounced awns that balance the unit as it falls. We discovered that the awns are also able to propel the seeds on and into the ground. The arrangement of cellulose fibrils causes bending of the awns with changes in humidity. Silicified hairs that cover the awns allow propulsion of the unit only in the direction of the seeds. This suggests that the dead tissue is analogous to a motor. Fueled by the daily humidity cycle, the awns induce the motility required for seed dispersal

1 Biomaterials Department, Max Planck Institute of Colloids and Interfaces, Golm, Germany.
2 Biotechnology Department, Tel Hai Academic College, Upper Galilee, Israel.

* Correspondence should be addressed to elbaum{at}mpikg.mpg.de (R.E.) or to fratzl{at}mpikg.mpg.de (P.F.)

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