You Can’t Fool a Venus Flytrap

It knows when you are trying to feed it something dead.

Venus flytrap trigger hairs are micronewton mechano-sensors that can detect small insect prey (Nature Plants). How did they learn this kind of science? Where are the brains, nerves and muscles that can move so quickly?

Venus flytraps detect moving insects via highly sensitive, action potential (AP)-producing trigger hairs, which act as high-sensitivity levers, crucial for prey capture and digestion. Controlled stimulation revealed that they can trigger APs for deflections >2.9°, angular velocities >3.4° s^–1 and forces >29 µN. Hairs became desensitized and subsequently responded to fast consecutive stimulations; desensitization increased at lower temperatures. Recording of ant trigger hair contact events revealed that even small insects exceed the hairs’ sensitivity threshold.

Venus flytrap (Jason, Flickr)

What Makes a Venus Flytrap Snap (The Scientist). This article summarizes the paper, and tells what German scientists found.

Just how the plants can tell dinner from debris was the question Scherzer’s group recently sought to answer by observing Venus flytraps in the lab. Using a tiny force meter in combination with electrophysiological recordings to capture action potentials, the researchers measured the trigger hairs’ responses to ants walking across the trap leaves. They reported in Nature Plants last year that the force applied to the trigger hairs didn’t matter so much as how far and how quickly they were bent. The plants responded to stimuli that were fast, like those from a wriggling insect. Too slow, and they ignored the movement. 

“This mechanism would ensure that it is something living that is inside the leaves, rather than something like a little piece of stick or other things that they are not interested in investing in digesting,” says Naomi Nakayama, who studies plant biomechanics at Imperial College London and was not involved in the project.

Nothing about evolution was said in the article or paper, even though Darwin wrote a book on Insectivorous Plants.