Leaves Rapidly Snap Shut

close up photograph of green bug on a venus flytrap

Biological Strategy

Venus flytrap

Alexandra Ralevski

Image: Mark Freeth / Flickr / Some rights reserved

Capture, Absorb, or Filter Organisms

Many living systems must secure organisms for food. But just as one living system must capture its prey to survive, its prey must escape to survive. This results in capture and avoidance strategies that include trickery, speed, poisons, constructed traps, and more. For example, a carnivorous plant called the pitcher plant has leaves formed into a tube that collect water. Long, slippery hairs within the tube face downward. When insects enter the tube seeking nectar, they lose their footing and slide inside, unable to climb out and escape being eaten and digested by the plant.

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Sense Touch and Mechanical Forces in a Living System

Perceiving touch enables living systems to detect other living systems around them and environmental conditions, such as air movement, water currents, and temperature. This ability can help them sense danger as well as opportunity, as when a Venus flytrap’s hairs sense the presence of an insect to eat. Sometimes, a living system senses touch or mechanical forces at a coarse scale; other times, at a sensitive scale that detects very subtle differences. For example, a human elbow is not nearly as sensitive to textures as human fingertips. Fingertips have dermal ridges and many nerve endings that increase sensitivity, enabling them to explore the environment in detailed ways. Elbows don’t need to sense at that level of detail.

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Flowering Plants

Clade Angiosperms (“receptacle seed”): Dandelions, oaks, grasses, cacti, apples

With 416 families containing some 300,000 known species, angiosperms are the most diverse group of plants, and they can be found around the globe in a wide variety of habitats. They are characterized by seeds that grow enclosed in ovaries, which are enclosed in flowers. The floral organs then develop into fruits of myriad kinds and dimensions, from simple seed casings on maples to elaborate fleshy growths like papayas. The oldest flower known from fossils, Montsechia vidalii, appeared during the Jurassic Period 130 million years ago. They are the primary food source for herbivorous animals, which in turn makes them the indirect food source for carnivores as well.

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The leaves of the Venus flytrap snap shut and trap prey within milliseconds by turning physical signals into electrical signals.

Carnivorous plants, such as the Venus flytrap (Dionaea muscipula), rely on nutrients from small prey animals when growing in nutrient-poor soil. When an unsuspecting prey brushes up against two touch-sensitive hairs on the inside of the trap-shaped leaves, the trap snaps shut, ensnaring the prey for later digestion.

The touch-sensitive hairs, known as trigger hairs, signal trap closure using sodium-activated action potentials (APs). An action potential is a way for cells to send information to one another in the form of an electrical signal. It occurs when positively charged ions, such as sodium, enter a cell and cause the electrical environment of the cell membrane to change until it reaches a certain threshold. After it reaches this threshold the cell “fires,” sending the electrical signal to another cell to activate a response.

In the case of the Venus flytrap, the two trigger hairs send a signal to the leaves to snap shut. Physical stimulation of one hair releases sodium ions into the hair cell, triggering the first action potential. Stimulating a second hair will release more sodium ions, triggering a second AP. Once two APs are elicited within 15-20 seconds of each other, these electrical signals stimulate motor cells in the leaves to snap the trap shut. This signal is incredibly fast, and the trap snaps shut within 100 ms of the triggering of the second hair.

Once the prey is captured it struggles to escape, continuously brushing more trigger hairs that fire more action potentials. These signals are sent to glands that line the leaves, which release enzymes to digest the prey. The prey is loaded with essential nutrients, including sodium, and its digestion provides a source of new sodium ions to trigger the next action potential to capture the plant’s next victim.

To learn more about how the Venus flytrap’s leaves power movement, check out this related strategy.

This strategy was contributed by Alexandra Ralevski.

Image: che / Wikimedia Commons / CC BY SA - Creative Commons Attribution + ShareAlike

Open Venus flytrap

Image: Original uploader was Bouba at fr.wikipedia / Wikimedia Commons / GFDL - Gnu Free Document License

Venus flytrap with open trap displaying trigger hairs

Image: Kaim-Martin Knaak / Wikimedia Commons / CC BY SA - Creative Commons Attribution + ShareAlike

Venus flytrap captures prey

Image: Stefano Zucchinali / Wikimedia Commons /

A dionea muscipula has just caught a wasp.

Image: Stefano Zucchinali (Ste3986) / Wikimedia Commons / CC BY SA - Creative Commons Attribution + ShareAlike

Digested fly in a Dionea muscipula trap

Stretched Leaves Power Rapid Closure

Venus flytrap

Stretched leaves of the Venus flytrap power rapid trap closure by storing mechanical energy.

Last Updated May 1, 2017

References

“The rapid closure of the Venus flytrap (Dionaea muscipula) leaf in about 100 ms is one of the fastest movements in the plant kingdom. This led Darwin to describe the plant as ‘one of the most wonderful in the world’. The trap 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 action potentials in the leaves.” (Forterre 2005:421).

Journal article

How the Venus flytrap snaps

Nature | 01/01/2005 | Forterre, Yoel; Skotheim, Jan M.; Dumais, Jacques; Mahadevan, L.

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Reference

“When an insect visits the trap and tilts the mechanosensors on the inner surface, action potentials (APs) are fired. After a moving object elicits two APs, the trap snaps shut, encaging the victim. Panicking preys repeatedly touch the trigger hairs over the subsequent hours, leading to a hermetically closed trap, which via the gland-based endocrine system is flooded by a prey-decomposing acidic enzyme cocktail” (Böhm et al. 2016:286).
“We have demonstrated that the mechanical energy is received at the multicellular trigger hair and converted into an electrical signal, an AP. The APs originating from the trigger hair on one lobe travel through the entire trap to reach two major targets: (1) the motor tissue, which initiates fast trap closure and the formation of the green stomach, and (2) the glands, the endocrine system responsible for the prolonged processing of the nutrient and sodium-rich animal meal.” (Böhm et al. 2016:291).

Journal article

The Venus flytrap Dionaea muscipula counts prey-induced action potentials to induce sodium uptake.

Current Biol. | 01/01/2016 | Böhm J, Scherzer S, Krol E, Kreuzer I, von Meyer K, Lorey C, Mueller TD, Shabala L, Monte I, Solano R, et al.

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