Provoking a Venus flytrap requires a certain finesse. If you brush just one of the trigger hairs on the inside of its leaves, the plant probably won’t react. But if you snap it back fast enough, it’ll spring into action, shutting its famous mouth.
Waiting for a double trip probably prevents the plant from wasting energy on raindrops or other things that aren’t nutritious flies. But despite centuries of interest in the species, no one was quite sure how plants remembered the first trigger to act on a second.
In an article published last week in Nature Plants, researchers reported finding the cause: calcium ions. By getting the traps to glow when the calcium entered their cells, a team of scientists was able to show how the ions build up when the hairs are triggered, eventually causing the popping.
In 1988, a couple of plant scientists speculated that two overlapping streams of calcium ions could have prompted the Venus flytrap to shut down, but they haven’t had a chance to test their idea. More recently, another group of researchers – including Rainer Hedrich, who participated in the new paper – solved part of the puzzle by showing that electrical signals tell the flytrap when its trigger hairs have been pressed. They also speculated that calcium helps the plant keep track.
To visualize the flytrap’s memory mechanism, Dr. Hasebe and his colleagues inserted a special type of gene into the plant. This gene, widely used in biology, produces a protein that fluoresces green when it binds to a target, in this case a calcium ion.
Hiraku Suda – the article’s lead author and a doctoral student in Dr. Hasebe’s lab at the time of the research – was tasked with integrating the gene, which required infecting the plant’s leaves with a modified bacterium and then using those leaves. to grow new shoots. .
It took him two and a half years to figure it out. The key, it turned out, was growing the plants in the dark, which may have made them easier to infect with bacteria. When it finally worked, he was so excited, “I haven’t slept in a week,” he said.
Subsequently, the researchers began targeting the plant. After a single touch on a sensory hair, a green blush appeared at the base of the hair and quickly spread through the leaves, indicating a surge of calcium ions.
A second touch within about 30 seconds caused another surge, pushing the total amount of calcium past a threshold that caused the trap to close. (In the experiment videos, the eye-catching flytrap looks like the entrance to a fun carnival house.) But if the researchers waited too long between taps, concentration dropped again and the trap didn’t move.
“Being able to actually see the start of the calcium wave in the deflected hair and travel through the leaf is truly amazing,” she said. Ueli Grossniklaus, a plant biologist from the University of Zurich who was not involved in the research. Earlier this year, Dr. Grossniklaus helped show that in some cases, a single slow detour of a hair can also cause flytrap to close. He said further research into how calcium and electrical activity relate, and the strength and speed of the trigger strokes, would further illuminate the plant’s functioning.
Dr Suda, now a postdoctoral fellow at Saitama University in Japan, intends to use his new method to study prey capture, digestion and other flytrap activities. They are “beautiful plants,” he said. “I can always ask new questions by seeing them.”