Scientists have solved a long-standing mystery about how Venus flytraps achieve their lightning-fast closure, answering questions that puzzled Charles Darwin and researchers for more than a century. A new study reveals that the plant uses a sophisticated mechanism involving rapid changes to cell wall properties rather than hydraulic pressure alone.
When an insect triggers the trap's sensitive hairs, the plant responds by softening the cells on the outer surface of its leaves. This cellular change causes the leaf to flip into a closed position in less than 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 and senior author of the research. "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."
The research team conducted intricate experiments to measure the leaf's physical properties during the snapping process. Since triggering the trap causes immediate closure, researchers faced a significant challenge in taking measurements. They solved this by immobilizing the plant's leaves using dental glue, allowing them to activate the trap while keeping it stationary.
Using a device called a nanoindenter, scientists poked the leaf's outer surface to measure its stiffness. They discovered that immediately after activation, the leaf surface became noticeably softer. This finding contradicted the previous leading hypothesis, which suggested that water movement within the leaf caused the snap. Instead, the cells themselves were becoming more flexible.
The mechanism resembles how a dome-shaped rubber popper toy spontaneously flips when pressed against a surface. Forterre explained that this type of rapid mechanical property change is unusual in the plant world. "I'm not aware of any other plants with this kind of very rapid change of mechanical properties of the cells," he said.
Forterre first became interested in Venus flytrap mechanics two decades ago when a colleague brought one into the laboratory. As a physicist, he wanted to understand the forces and mechanisms driving the movement. He noted that the research reveals broader truths about plant capabilities: "Plants are just amazing. It makes you realise how all plants can sense their surroundings, transport information, react, defend themselves, feed."
The findings were published in the journal Science and represent a significant advance in understanding how plants can perform rapid movements without muscles or nervous systems. The discovery could potentially inspire new applications in soft robotics and bio-inspired engineering.