To trap its prey, the Venus flytrap sends rapid electrical impulses, which are generated in response to touch or stress. But the molecular identity of the touch sensor has remained unclear. Japanese scientists have identified the molecular mechanism that triggers that response and have published their work in a new paper in the journal Nature Communications.
As previously reported, the Venus flytrap attracts its prey with a pleasing fruity scent. When an insect lands on a leaf, it stimulates the highly sensitive trigger hairs that line the leaf. When the pressure becomes strong enough to bend those hairs, the plant will snap its leaves shut and trap the insect inside. Long cilia grab and hold the insect in place, much like fingers, as the plant begins to secrete digestive juices. The insect is digested slowly over five to 12 days, after which the trap reopens, releasing the dried-out husk of the insect into the wind.
In 2016, Rainer Hedrich, a biophysicist at Julius-Maximilians-Universität Würzburg in Bavaria, Germany, led the team that discovered that the Venus flytrap could actually "count" the number of times something touches its hair-lined leaves—an ability that helps the plant distinguish between the presence of prey and a small nut or stone, or even a dead insect. The plant detects the first "action potential" but doesn't snap shut right away, waiting until a second zap confirms the presence of actual prey, at which point the trap closes. But the Venus flytrap doesn't close all the way and produce digestive enzymes to consume the prey until the hairs are triggered three more times (for a total of five stimuli).
