The Venus Flytrap
The rapid closure of the carnivorous plant Venus
flytrap (Dionaea muscipula) is one of the
fastest motions (typically 100 ms) in the plant kingdom
and led Darwin to describe the plant as "one of the
most wonderful in the world". The closure is initiated
by the mechanical stimulation of trigger hairs. Previous
studies have focused on the biochemical response of
the trigger hairs to stimuli and quantified the propagation
of an action potential in the leaves. We complement
these studies by considering the post-stimulation mechanical
aspects of Venus flytrap closure. Using high-speed
video imaging, non-invasive microscopy techniques and
a simple theoretical model we show that the fast closure
of the trap results from a snap-buckling instability.
Our study illuminates an ingenious solution to scaling
up movements in non-muscular engines and provides a
general framework for understanding nastic motion in
of the open and closed leaves of the Venus flytrap.
The glass needle in the foreground was used to
trigger the closure. Note that the leaves flip
by almost turning inside out - similar to the
flipping of a contact lens, plastic lid or the
reversal of a torn tennis ball.
versions of the leaves, showing the change in
shape associated with closure of the leaf. Cutting
a leaf parallel to the midrib and perpendicular
to it shows that the snapping is in fact driven
by just curvatures changes in the direction perpendicular
to the midrib.
The dots were
used to track the motion of the leaf as a function
of time. Especially note how the curvature of
the leaf changes so quickly. The glass rod on
the right plays the role of the "fly".
see the high-resolution version. Courtesy of
Forterre and Mahadevan.
and courtesy of Farrah Shindler.
|Click here to
see a Quicktime movie of the
flytrap in action.
of Mahadevan et. al.
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Flytrap - Leader in Biometrics? Newswatch
teach big lessons about how to get going, 16 June 2005