Scientists unlock the secret behind the Venus flytrap’s snap

By Will Dunham

June 11 (Reuters) – Shame on the poor fly that landed on the Venus flytrap. When the insect touches the hair-like structures on this remarkable carnivorous plant, its trap snaps shut, dooming the victim to be digested by secreted enzymes for several days. Scientists have now found the physical mechanism behind this breaking action.

The researchers said experiments showed that the closure of the Venus flytrap is initiated by a rapid softening of the cell walls in the plant’s outer layer, a highly modified leaf divided into two hinged lobes that resemble jaws with teeth.

The prevailing hypothesis for more than a century was that closure of the trap occurred by a rapid redistribution of water within the leaf, as water moved between cells, swelling one side of the leaf. New research points to a different biological mechanism.

“One of the world’s most iconic plants can still surprise us. After more than a century of research, we are discovering fundamentally new things about how the Venus flytrap works,” said physicist Yoël Forterre of the French research agency CNRS and Aix-Marseille University, senior author of the study published Thursday in the journal Science.

The Venus flytrap is a small carnivorous plant native to a limited area of ​​North Carolina and South Carolina in the United States. Like many carnivorous plants, it grows in nutrient-poor environments and supplements its diet by capturing and digesting insects.

In experiments conducted in Marseille, researchers used high-speed imaging, mechanical measurements and mechanical modeling by indentation of the plant’s outer layer. They also measured water transport within the plant tissue to rule out that mechanism was involved.

Forterre said, “The plant uses special trigger hairs on the inner surface of the trap. When an insect touches these hairs twice in a short time, the trap closes. Closing can occur in as little as a tenth of a second.” he said.

“Our hypothesis is that the trap is mechanically loaded, like a spring, before it is triggered. When the trap is stimulated, the cell walls of the outer epidermal layer rapidly soften by roughly 30% to 40%, meaning the cell wall becomes more flexible. This releases internal stresses stored in the tissue and causes the trap to bend and close. Softening occurs in about a second,” Forterre said.

Once the trap is closed, the insect is sealed inside for digestion.

“By directly measuring the response mechanism of the living trap, we pinpointed the internal ‘motor’ that drives the leaf towards the instability threshold and initiates the sudden bending that closes it,” said Jeongeun Ryu, a physicist and lead author of the study who worked on the research as a postdoctoral researcher at CNRS and Aix-Marseille University.

After the plant absorbs the nutrient-rich fluid produced by its digestive processes, the trap reopens, leaving behind the insect’s empty exoskeleton.

“What I find remarkable is that evolution often does not invent completely new mechanisms, but rather reuses and improves existing ones. Plants are known to change the mechanical properties of their cell walls during growth, but the Venus flytrap seems to push this mechanism to the extreme, using it on a time scale of about one second,” Forterre said. he said.

There are approximately 800 known species of carnivorous plants. They are not all closely related, suggesting that meat-eating evolved independently many times during plant evolution.

How the Venus flytrap closes has long been of interest to scientists, including Charles Darwin, the 19th-century naturalist who developed the theory of evolution by natural selection. The researchers see potential practical applications from their findings.

“To our knowledge, this is the first time such a rapid change in the mechanical properties of cell walls has been seen in a plant,” Ryu said.

“This solves the question, dating back to Darwin, of what drives one of the fastest movements in the plant kingdom, and points to a new way for a living being to move: not by pumping liquid or simply collapsing, but by actively adjusting the hardness of its own material. This principle could eventually inspire soft robots or smart materials, but this remains a longer-term prospect,” Ryu said.

(Reporting by Will Dunham in Washington; Editing by Daniel Wallis)