Science · Biology

Venus flytrap

Named 1768

Biology — carnivorous plants

The Venus flytrap is a small carnivorous plant whose leaves end in a hinged, two-lobed trap fringed with interlocking spines. Each lobe carries trigger hairs; touching one fires an electrical signal through the leaf, and a second touch within about twenty seconds snaps the trap shut in roughly a tenth of a second — among the fastest movements in the plant kingdom. Continued struggling by the prey drives further signals, and the plant in effect counts them: around five turn on the digestive glands and the machinery for absorbing the meal. Darwin, who devoted a chapter of Insectivorous Plants to it, called it the most wonderful plant in the world. Despite its worldwide fame as a houseplant, it grows wild only in a narrow band of boggy coastal plain around Wilmington, North Carolina.

How to spot them

▸A hinged two-lobed trap fringed with interlocking spines, sprung by touch-sensitive hairs
▸Darwin called it 'the most wonderful plant in the world'
▸Closes in about a tenth of a second, and counts the touches before it digests
▸Wild only within about a hundred kilometres of Wilmington, North Carolina
▸The sole species in its genus, related to the sundews

Key facts

Darwin called it 'the most wonderful plant in the world' and gave it a chapter of Insectivorous Plants (1875)

He first used the phrase in a letter to Asa Gray in 1860

Two touches on its trigger hairs within about twenty seconds spring the trap

A single touch is ignored, so raindrops and windblown grit do not waste a closure

It counts electrical signals: about five tell it to switch on its digestive glands (2016)

Böhm and colleagues showed the count controls jasmonate signalling and sodium uptake

Its specific epithet is Latin for 'mousetrap', and its genus honours the mother of Aphrodite

Named by the London merchant-naturalist John Ellis in 1768; Dione was Aphrodite's mother

It grows wild only in a narrow band of boggy coastal plain around Wilmington, North Carolina

Poaching from the wild became a felony there in 2014

The lobes shut in about a tenth of a second by snapping from convex to concave, like a tiddlywink (2005)

Forterre and colleagues, in Nature, explained the speed as elastic buckling of a bistable surface

Despite its name, most of its prey is crawling spiders, ants and beetles

Flying insects are a minority of the catch

Key ideas

Carnivory is a nitrogen strategy, not a source of energy: the plant photosynthesises normally, but grows in nutrient-poor acid bog where insects are a better source of nitrogen and phosphorus than the soil.
Snap-buckling: the closed lobes are held under elastic strain, so once the trigger releases them they flip through an unstable state from convex to concave. The movement is powered by stored elastic energy rather than by muscle-like growth, which is why it can beat the usual speed limits on plant movement.

Quick-fire facts

•Dionaea muscipula J.Ellis, 1768; the only species in the genus Dionaea
•Family Droseraceae, with the sundews (Drosera) and the aquatic waterwheel plant (Aldrovanda)
•Each lobe usually bears three trigger hairs; two stimulations within roughly 20–30 seconds close the trap, and about five switch on digestion
•The signal is a genuine action potential, first recorded in the plant by Burdon-Sanderson in 1873 at Darwin's prompting
•Digestion takes about a week to ten days, after which the trap reopens; an individual trap can catch only a handful of meals before it dies
•It is native to a small area of the Carolinas, mostly within about 100 km of Wilmington, North Carolina, and is grown in tens of millions by tissue culture worldwide
•Plants need winter dormancy, acid nutrient-poor soil and rainwater or distilled water; tap water kills them
•Fire is essential to its wild habitat, clearing competing shrubs from the longleaf pine savannah
•It became the official state carnivorous plant of North Carolina in 2005
•Common misconception: feeding it hamburger or repeatedly triggering empty traps harms the plant, and the traps are never large enough to threaten anything bigger than an insect

Drill it — 10 cards

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Sources

Jennifer Böhm et al., Current Biology 26 (2016) — The Venus flytrap Dionaea muscipula counts prey-induced action potentials to induce sodium uptake
Yoël Forterre, Jan M. Skotheim, Jacques Dumais and L. Mahadevan, Nature 433 (2005) — How the Venus flytrap snaps
Charles Darwin — Insectivorous Plants 1875; chapters 13–15 cover Dionaea