It's really thrilling and awe-inducing to watch a carnivorous plant perform its special ability. These special plant species have evolved over time. Because they live on soil devoid of nutrients, they developed strange and fascinating feeding mechanisms.
In other words, carnivorous plants can "eat" prey, including insects and other arthropods, in order to get their much-needed nitrogen intake. Scientists say there have been some instances when larger carnivorous plants managed to consume small frogs, birds or snakes.
How do carnivorous plants feed themselves? A carnivorous pitcher plant traps its prey within a rolled leaf containing juice of digestive enzymes, which are similar to the ones on our stomach. It lures its prey with a sweet-smelling scent first before consuming it.
On the other hand, a Venus flytrap, one of the first carnivorous plants we learn in grade school, uses snap traps or some kind of mouse trap which quickly close when the sensitive hair on the plant's leaf lobes are triggered. This plant can only open and close a few times before it dies.
The Theory Of Natural Selection
Charles Darwin once wrote the first well-known dissertation on carnivorous plants and related the strange feeding mechanisms of these plants to his theory of natural selection. This theory, which is a key mechanism of evolution, focuses on the different survival and reproduction of living things.
The book titled "Insectivorous Plants" records Darwin's experiments with several carnivorous plants. He paid specific attention to the adaptations that allow the plants to survive in different and often harsh conditions.
Modern research has allowed for the continuation of Darwin's studies on carnivorous plants.
For instance, although carnivorous pitcher plants are brainless, a study published in January 2015 revealed that these plants adopt a remarkable strategy to catch their prey.
The plant cannot use thinking skills, of course, but because of natural selection, the pitcher plant can sporadically capture large numbers of ants.
How can it do that? The pitcher plant uses its rim, which becomes slippery when the trapping surface of the plant is wet.
But when the trapping surface is dry, the rim also turns dry, rendering it unusable. So during sunny and hot days, the pitcher plant's trap is "switched off" for up to eight hours. At this time, the plant does not catch any prey.
When researchers artificially kept the trapping surface wet, they found that the pitcher plants were no longer able to catch batches of ants.
Somehow, the explanation is simple. Remember the sweet-smelling scent we mentioned? When an individual scout ant locates a pitcher plant with this sweet-smelling juice, the ant goes back to the colony to call for more ant workers.
When the trap is extremely slippery, the plant traps the first individual scout ant, and it can no longer recruit other ant workers.
However, when the plant switches off its traps sometime during the day, the scout ants can return to their colony and invite other ants. This batch of ants get trapped in one sweep once the plant's rim gets wet.
"Natural selection is very relentless and will only reward the most successful strategies," said Ulrike Bauer, biologist from the University of Bristol and lead researcher of the study.
The Venus Fly Trap's 'Math Skill'
For Venus fly traps, the key to catching their prey is their snap trap's quick response and sensitivity to insects.
Turns out, there's some kind of strategy behind that as well. A new study featured in the journal Current Biology revealed that Venus fly traps can actually count.
The Venus fly trap has to retain a lot of energy to perform the task of closing its mouths shut. It has to make sure that when an insect is stepping on its surface, the insect has stayed long enough for the plant to consume it.
How will the Venus fly trap know? When the insect has brushed up two times against the plant's trigger hairs, the Venus fly trap snaps shut in a blink of an eye. This occurs due to electrical impulses called "action potentials" or APs.
With two APs within 20 seconds, the plant can identify its prey and lock it in. A third AP allows the plant to figure out what kind of insect it has to take in. By the fifth AP, the Venus fly trap starts to chemically salivate, picks up sodium from the prey and digests its needed nutrients.
Strangely, if the insect stopped moving after coming into contact with the plant's surface, the digestive process of the Venus fly trap theoretically stops as well, opens its mouth again, enabling the prey to get out. If the insect, however, flails about and triggers the digestive process once again, it will meet its end this time.
Photo: Peter Shanks | Flickr