Scientists have uncovered the mechanism behind the Venus flytrap's lightning-fast snap, resolving a puzzle that stumped Charles Darwin and generations of researchers. The carnivorous plant, which lures insects with nectar before capturing them, achieves its rapid closure by softening cells on the outer surface of its leaves.
Hair-Trigger Detection Leads to Cell Softening
In a series of intricate experiments, researchers found that when an insect triggers the plant's sensitive hairs, an electrical signal spreads across the leaf within a tenth of a second. This signal causes cells on the outer surface to become more flexible, prompting the trap to flip shut in under a second.
“When Darwin saw these plants move so fast, he was convinced that the plant had a muscle inside, but plants do not have muscles and they do not have nerves,” said Dr. Yoël Forterre, a physicist at the French National Centre for Scientific Research (CNRS) and Aix-Marseille University, and senior author of the study. “For more than a century there have been many hypotheses. It’s very surprising that plant cell walls can tune their mechanical properties so fast.”
Overcoming Measurement Challenges
A major challenge was measuring the physical properties of a system that moves so quickly. “As soon as you perturb it, it closes,” Forterre explained. To overcome this, the team carefully immobilized the leaves using dental glue, allowing the trap to be triggered without moving. They then used a nanoindenter—a metal tip that pokes the leaf surface—to measure stiffness, akin to poking a balloon with a finger.
The results showed that the outer surface softened immediately after activation. Measurements of leaf topology revealed that this softening was due to cells becoming more flexible, not from water movement as previously thought. The mechanism resembles how a dome-shaped rubber popper toy flips when pressed.
“I’m not aware of any other plants with this kind of very rapid change of mechanical properties of the cells,” Forterre said.
A 20-Year Obsession
Forterre’s fascination with the Venus flytrap began two decades ago when a colleague brought one into the lab. “As a physicist, I thought we should understand the motor, the forces,” he said. “I’ve been obsessed by this for 20 years.” He added, “Plants are just amazing. It makes you realise how all plants can sense their surroundings, transport information, react, defend themselves, feed.”
The findings are published in the journal Science.
