How a Venus flytrap snaps up its victims
- 29 January 2005
- From New Scientist Print Edition. Subscribe and get 4 free issues.
A VENUS flytrap snaps shut faster than you can blink. And now we know why. Whereas our sluggish movements are the result of muscles contracting, the plant snaps shut in the way that a torn tennis ball flips inside out.
When Lakshminarayanan Mahadevan of Harvard University and his colleagues used a high-speed camera to film the leaves closing, they noticed that the curvature of the leaves flipped from convex to concave as the trap closes. The transformation takes just one-tenth of a second. They reasoned that the leaves were snapping from one stable shape to another - a movement that can occur much faster than muscle contraction.
Although they do not yet know what happens at the cellular level, they have devised equations that describe the mechanical action (Nature, vol 433, p 421). From the shape of the leaves, these predict whether the trap is able to shut, how soon after an insect lands it will start to close, and how fast the leaves will move. "Our model makes simple predictions based on experiments, and then further experiments bear these out," Mahadevan says.
Darwin was fascinated by the plant. "Our study still leaves us baffled about one question that motivated him - how did this mechanism evolve?" Mahadevan says.
