Some horror movies love to feature man-eating plants. Whether the hungry plant is stumbled upon by intrepid explorers deep in shadowy jungles, discovered on a wild and dangerous alien planet, or hidden in the back of a florist shop managed by a mad proprietor, the potential victim often deems to be a scantily clad blonde who can scream better than she acts.
That’s Hollywood. In the real world, meat-eating plants do exist, but most are small, barely bigger than the palm of a hand. They are, however, no less voracious than their celluloid brethren that made throngs of kids squeal with fright during Saturday morning matinees. [See Addendum A]
Of the many types of carnivorous plants, perhaps none is better known than the Venus flytrap (Dionaea muscipula). [Photo]
A strangely compelling plant, the flytrap works its magic on such unsuspecting victims as smaller insects and arachnids. It doesn’t obtain all its nourishment from small prey, however, it also draws sustenance from the air, sunlight and nutrients in soil.
Because the flytrap lives in marshes and boggy areas, nutrients are in short supply so they plants gradually evolved into part-time meat-eaters to supplement their overall diet.
Darwin’s secret “love affair”
Naturalist Charles Darwin loved studying carnivorous plants.
Don Waller, a botanist at the University of Wisconsin, notes, “Darwin was fascinated by carnivorous plants in general and the Venus flytrap in particular, I think, partly because they go against type.”
When most people think of a plant they might picture a nice shade tree, a rose, or a potted philodendron sitting in a corner of an office. But carnivorous plants are different; they stir the imagination and bring a sense of surprise and wonder. They also appeal to people’s latent tendency towards the macabre. If Edgar Allen Poe had a plant sitting on the desk where he penned his tales of horror, it could have been a Venus flytrap.
“In his [Darwin’s] time and ours, most of us feel that plants are passive, harmless, and can’t move. But the Venus flytrap acts like an animal, it moves fast and eats fresh meat,” Waller explains.
In the United States, the Venus Flytrap is indigenous only in the marshy areas of two states: North and South Carolina. Because so many have been collected over the years, few grow in the wild anymore and are cultivated in greenhouses with lots of light, water, boggy soil and, of course, fat flies.
How it traps its meal
Venus Flytraps have wide, convex leaves that spread open invitingly. The leaves wait like open arms inviting unsuspecting flies, bees, beetles and spiders to it. The inside of the leaves are blanketed with sensitive bristles that are called trigger hairs. When the plant’s next meal unsuspectingly trips enough of those hairs the leaves snap closed like a bear trap imprisoning whatever it is that set off the trigger mechanism.
Research has revealed that the trap can close in as little as one-third of a second.
The leaves don’t close completely at first. Botanists suspect the plant delays sealing the leaves into a digestive bladder to allow sufficient time for smaller insects to escape. This is nature’s approach to conservation of energy: too small of a meal would expend more energy digesting it that its worth.
Larger insects are invited to dinner—the Venus flytrap’s dinner. The long spine-like appendages called cilia that encircle the perimeters of the leaves will effectively keep larger insects and arachnids inside. They act like a plant’s version of teeth.
After several minutes the trap closes itself completely creating an air-tight seal. By doing this, the flytrap contains the meal, its digestive secretions, and keeps out bacteria and other predators that would compete for the carcass as food. It also protects the digestive process from rain that might otherwise wash away the nutrients it was absorbing.
Once the leaves are sealed into a digestive pouch, the important business begins. The doomed meal, unable to escape its deathtrap, is slowly and inexorably dissolved by secretions similar to the ones produced by the human digestive system.
Because the skeletons of insects and arachnids are on the outside, not inside. This exoskeleton cannot be digested by the flytrap. When the digestive process is completed after 5 to 12 days the leaf reopens and expels the remains.
The size of the meal, atmospheric pressure, humidity, ambient temperature, age of the leaves and frequency of past feedings all play a part in hiow long it takes for the trap to reopen and reset.
If what set off the trap is not potential food, such as drifting seeds or tiny pebbles, the trap will reopen itself withing 12 hours and expel the detritus.
Scientific research has revealed some of the mechanism that permits the Venus flytrap to close with the speed it exhibits. Yet, the plant does not have any muscles, tendons or nervous system like animals have. This has puzzled botanists who theorize that some hydrodynamic process incorporating fluidic pressure responds to the stimulus of its trigger hairs and activates an electrical current that sets each half of the leave entrapment system into motion. For a more detailed synopsis of the hard science behind this process, please see the short addendum following the end of the article. [Addendum B]
Origins of plant finally discovered
According to research from botanists, the Venus flytrap had its origins in a similar plant with sticky leaves. As the plant evolved to adopt to the changing environment, it developed a need to supplement its diet and responded with novel additions such as the cilia and the super-sensitive trigger hairs.
Botanist Ken Cameron of the University of Wisconsin conducted a DNA analysis of the Venus flytrap and its closest relative, the waterwheel plant. Like the flytrap, the waterwheel is carnivorous. Cameron confirmed that the two plants are genetically associated and that their common ancestor is an ancient species named Drosera regia.
As time progressed the plants’ need to trap and ingest larger insects drove its evolution forward to the modern day version we can purchase today in florist shops and some department and grocery stores.
Links
“The Venus flytrap”
“Venus flytrap origins uncovered”
Video: “Venus flytrap in action”
Addendum A: “Feverish nightmares”
A Filipino movie released in the early 1960s featured a female mad scientist whose jungle “research” lab developed a strain of 7-foot Venus flytraps.
A poor man’s version of “The Day of the Triffids,” the mobile plants scuffled about, responded to their mistress’s shrill commands, and prepared themselves to invade Manila. Why the scientist wanted her mutated carnivorous plants to invade the Philippines’ capital city was never made clear. But the movie, no doubt originally produced in the language of Tagalog, was dubbed in English and featured such memorable lines as, “Follow me, my lovelies,” and “We’ll kill them; we’ll digest them all!”
One can imagine the screenwriter pecking out his feverish nightmares on an old-fashioned typewriter in a nondescript apartment the size of a modern day walk-in closet.
The scientist, and her army of gigantic Venus flytraps, all perished in a raging fire during the last reel.
Addendum B: Scientific explanation (courtesy of Wikipedia)
Mechanism of trapping
The Venus Flytrap is one of a very small group of plants capable of rapid movement, such as Mimosa, the Telegraph plant, sundews and bladderworts.
The mechanism by which the trap snaps shut involves a complex interaction between elasticity, turgor and growth. In the open, untripped state, the lobes are convex (bent outwards), but in the closed state, the lobes are concave (forming a cavity). It is the rapid flipping of this bistable state that closes the trap, but the mechanism by which this occurs is still poorly understood. When the trigger hairs are stimulated, an action potential (mostly involving calcium ions—see calcium in biology) is generated, which propagates across the lobes and stimulates cells in the lobes and in the midrib between them. Exactly what this stimulation does is still debated. The acid growth theory states that individual cells in the outer layers of the lobes and midrib rapidly move 1H+ (hydrogen ions) into their cell walls, lowering the pH and loosening the extracellular components, which allows them to swell rapidly by osmosis, thus elongating and changing the shape of the trap lobe. Alternatively, cells in the inner layers of the lobes and midrib may rapidly secrete other ions, allowing water to follow by osmosis, and the cells to collapse. Both of these mechanisms may play a role and have some experimental evidence to support them.
Digestion
If the prey is unable to escape, it will continue to stimulate the inner surface of the lobes, and this causes a further growth response that forces the edges of the lobes together, eventually sealing the trap hermetically and forming a ‘stomach’ in which digestion occurs. Digestion is catalyzed by enzymes secreted by glands in the lobes.
Oxidative protein modification is likely to be a predigestive mechanism of the Dionaea muscipula. Aqueous leaf extracts have been found to contain quinones such as the naphthoquinone plumbagin that couples to different NADH-dependent diaphorases to produce superoxide and hydrogen peroxide upon autoxidation. Such oxidative modification could rupture animal cell membranes. Plumbagin is known to induce apoptosis, associated with the regulation of Bcl-2 family of proteins. When the Dionaea extracts were preincubated with diaphorases and NADH in the presence of serum albumin (SA), subsequent tryptic digestion of SA was facilitated. Since the secretory glands of Droseraceae contain proteases and possibly other degradative enzymes, it may be that the presence of oxygen-activating redox cofactors function as extracellular predigestive oxidants to render membrane-bound proteins of the prey (insects) more susceptible to proteolytic attacks.
Digestion takes about ten days, after which the prey is reduced to a husk of chitin. The trap then reopens, and is ready for reuse.
