Scientists have solved a biological puzzle that has mystified researchers for more than a century: exactly how does the Venus flytrap manage to snap its jaws shut so quickly when catching prey?
New research reveals that the carnivorous plant’s lightning-fast closure happens through a rapid weakening of cell walls in the trap’s outer surface. This discovery challenges the long-held theory that water movement within the plant drives the snapping mechanism.
The study shows that when an unsuspecting insect touches specialized trigger hairs inside the trap twice within a brief timeframe, the plant’s cell walls quickly become more flexible by approximately 30 to 40 percent. This softening releases built-up tension in the tissue, causing the modified leaf to bend and seal shut in as little as one-tenth of a second.
“One of the most iconic plants in the world can still surprise us. After more than a century of research, we are still 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 on Thursday in the journal Science.
The Venus flytrap grows naturally only in specific areas of North Carolina and South Carolina. Like other meat-eating plants, it thrives in environments with poor soil nutrients and supplements its diet by trapping and breaking down insects.
To conduct their investigation in Marseille, scientists employed high-speed cameras, mechanical testing of the plant’s surface layer, and computer modeling. They also tracked water movement within the plant tissue to eliminate that as the driving force.
“The plant uses specialized trigger hairs located on the inner surface of the trap. When an insect touches these hairs twice within a short period of time, the trap closes. Closure can occur in as little as one tenth of a second,” Forterre explained.
The researcher described the trap as being pre-loaded with mechanical tension, similar to a compressed spring waiting to be released.
“Our hypothesis is that the trap is already mechanically loaded before triggering, much like a spring. When the trap is stimulated, the cell walls of the outer epidermal layer rapidly soften by roughly 30 to 40%, meaning that the cell wall becomes more flexible. This releases internal stresses stored in the tissue and causes the trap to bend and close. The softening develops within about one second,” Forterre said.
Once trapped, the insect becomes sealed inside where digestive enzymes break it down over several days.
“By directly measuring the mechanics of the living trap as it responds, we pinned down the internal ‘motor’ that drives the leaf across its instability threshold and sets off the snap-buckling that closes it,” said physicist and study lead author Jeongeun Ryu, who worked on the study as a postdoctoral researcher at the CNRS and Aix-Marseille University.
Following digestion, the trap opens again, leaving behind only the insect’s hollow outer shell while the plant absorbs the nutrient-rich liquid.
The findings impressed researchers with how evolution adapts existing biological processes for new purposes.
“What I find remarkable is that evolution often does not invent entirely new mechanisms, but rather reuses and refines existing ones. Plants are known to modify the mechanical properties of their cell walls during growth, but the Venus flytrap appears to push this mechanism to an extreme, using it on a timescale of about one second,” Forterre said.
Scientists have identified approximately 800 different carnivorous plant species worldwide. These plants aren’t closely related to each other, suggesting that meat-eating behavior developed separately multiple times throughout plant evolutionary history.
The Venus flytrap’s snapping mechanism has fascinated scientists including Charles Darwin, the 19th century naturalist who developed the theory of evolution by natural selection. The research team believes their findings could lead to practical applications.
“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.
“It settles a question that goes back to Darwin – what drives one of the fastest movements in the plant kingdom – and points to a new way for a living thing to move: not by pumping fluid or simply collapsing, but by actively tuning the stiffness of its own material. That principle could eventually inspire soft robots or smart materials, though that remains a longer-term prospect,” Ryu said.
