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Botanical ratchets
I M Kulić1, M Mani, H Mohrbach
1Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA. kulic@seas.harvard.edu
Proceedings. Biological Sciences
|March 28, 2009
Summary
Nature
Area of Science:
- Biophysics
- Plant biology
- Mechanics
Background:
- Ratcheting surfaces, found in nature like plant awns, aid seed dispersal.
- These structures exhibit anisotropic (directional) properties.
Purpose of the Study:
- To investigate how anisotropically toothed surfaces act as motion rectifiers.
- To determine the relationship between awn length and ratchet efficiency.
Main Methods:
- Two simple model experiments were conducted.
- Theoretical analysis was combined with experimental data.
Main Results:
- Anisotropically toothed surfaces function as natural motion rectifiers.
- A linear relationship was found between awn length and ratchet efficiency under biologically relevant conditions.
Conclusions:
- Grass awns convert environmental stresses (e.g., humidity) into directed motion.
- Awn length acts as a fluctuation amplifier, providing a selective advantage in plants.
