Study

How the Venus flytrap snaps

Forterre, Yoël; Skotheim, Jan M.; Dumais, Jacques; Mahadevan, L.

Nature, 2005

Peer-reviewedphysiological studylaboratory

What they did

Traps were dotted with fluorescent markers and filmed closing at high speed, so the changing curvature of each lobe could be measured directly. The geometry was then modelled as an elastic shell held in a doubly curved, pre-stressed state.

Studied in: Dionaea muscipula
Sample size: traps filmed at high speed with the leaf surface marked

What they found

The lobes are held convex under elastic stress. A small active change in curvature carries the shell past a geometric instability, at which point stored elastic energy releases and the trap snaps through to concave in roughly a tenth of a second — far faster than water movement through plant tissue could achieve.

What it means

The authors' reading, and ours. Where they differ, that difference is the point.

How the authors put it

Closure is a snap-buckling instability, not a growth or turgor movement. The plant does the slow work in advance and spends it all at once.

How NatureHQ reads it

This is the answer to "how does a plant move that fast without muscles", and it is more interesting than a muscle would be. Plants move by shifting water, which is slow; the flytrap gets around the limit by storing elastic energy in the shape of the leaf and triggering a buckling instability, the same physics as a tennis ball turned inside out. The trigger hairs are not doing the moving. They are releasing something already loaded.

Limitations

A mechanical account of closure; it does not address how the electrical signal reaches the tissue.
Snap speed varies with trap age, temperature and hydration in ways the model simplifies.
Explains the fast shut, not the slow sealing and digestion that follow over hours.