We tend to think of the plant kingdom as a benign realm, where life is able to flourish without having to resort to the more base instincts found within many animals, such as killing for sustenance. Yet such a characterization would be entirely misleading because it would automatically exclude the nearly 600 known species of carnivorous plants which depend on trapping and killing their prey to survive.
These carnivorous plants have developed a multitude of different mechanisms for trapping their prey, ranging from snap traps (such as the Venus flytrap, which use rapid leaf movements to kill) to pitfall traps (where insects become trapped in a plant's slippery pitcher and are then broken down by digestive enzymes), but some of the most remarkable species make use of bladder traps. It is a truly remarkable trapping mechanism which allows some species of bladderwort to inhale their prey with a force that is over 600 times the acceleration due to gravity, but scientists are at a loss to describe how this mechanism actually works.
In a recent review in AoB Plants, Simon Poppinga and his colleagues from the Plant Biomechanics Group at the University of Freiberg outlined the state of research investigating the physics of the bladderwort, which is capable of achieving incredibly fast movements without the aid of muscles or nerves.
"The bladderwort traps are considered as some of the most complex structures in the plant kingdom," said Poppinga in a press release. "They are tiny, they are ultrafast in their sucking motion and they are complicated to investigate. There are still many mysteries about how these devices function. With our review we aimed at putting all relevant biophysical and structural information together and to inspire further research on these enigmatic devices."
Bladder traps are exclusive to a genus of aquatic and terrestrial plants known as bladderworts. The way a bladderwort works is by constantly pumping out the water from its bladder, which creates a partial vacuum within the bladder. This vacuum causes the walls of the bladder to be sucked in, which stores potential energy much like a spring. At this point, the bladder trap is set and all it needs is for an unlucky invertebrate to trigger on of the 'levers' which extends from the bottom of the bladder's trap door. This causes the seal on the bladder to break, releasing the potential energy and causing the bladderwort's prey and some water to be sucked into the bladder, where it is broken down with digestive enzymes secreted by the plant.
The entire trapping process only takes 1/100 of a second, and this lightning fast speed has made studying the mechanisms at work a very difficult process so far. Yet as Poppinga and his colleagues note, recent advancements in microscopy and faster cameras have allowed for greater insight into how the bladderwort is able to suck so hard."The great advantage of using modern microscopes … is that we could get a very close look at fine structures that are crucial for trap functioning," said Poppinga. "We could get architectural information in more detail than anyone has seen before. If we can work out how the bladderwort can grab food so quickly, it could also … possibly lead to biomimetic technical innovations."