Meat-eating plants have captured the imagination of many writers and filmmakers. One of the more well-known carnivorous plant stories is Little Shop of Horrors, which was originally filmed in 1960, then made into a Broadway musical, with a second Hollywood release in 1986. This comedy/musical/horror film tells the story of a florist clerk who discovers an unusual plant with a unique appetite… for human blood.
This got me to thinking about my vegetarian friends. I wonder, would they feel differently about eating a plant if they knew that the plant had eaten meat before it was harvested? Would a vegetarian eat a carnivorous plant?
Out of all of the strange plants in all the world, who would have thought that you would ever find flesh eating plants? Okay, maybe ‘flesh eating’ is a bit over the top, but there are insect eating plants out there, not man-eating – but carnivorous none the less.
All carnivorous plants are to be found in areas where the soil has very little nutrient content. These fascinating plants are categorized as carnivorous because they trap insects and arthropods, produce digestive juices, dissolve the prey, and derive some or most of their nutrients from this process. The first book on these plants was written by Charles Darwin, in 1875, titled Insectivorous Plants. After further discoveries and research, it is now believed that these marvels of the plant kingdom evolved independently six different times in five different orders of flowering plants, and nowadays these are represented by more than a dozen genera. They can be found throughout the world (except on Antarctica).
Many people are surprised to learn that the greatest variety of carnivorous plants can be found in North America. These plants inhabit bogs, rocky areas and other types of soils that are poor in nutrients. Carnivorous plants can survive at different altitudes and in various climates, but they do not tolerate dry habitats very well at all, so don’t expect to find them in the American Southwest.
A diet based on the flesh of animals provides carnivorous plants with the nutrients that other plants normally absorb from the ground. Carnivorous plants come in a wide variety of shapes and sizes but do use similar mechanisms to attract their prey. These plants are very popular and often cultivated because of their interesting morphology and unusual eating habits. Most species of carnivorous plants are small herbaceous plants that can reach up to about 12 inches in height. Some species look like bushy vines while others might seem more like an iris on steroids! They can grow to the height of 3 feet.
Most carnivorous plants eat flying, foraging, or crawling insects. Those that live in or around water capture very small aquatic prey like mosquito larvae and tiny fish. On rare occasions, some tropical carnivorous plants have even been reported to capture frogs, or even rats and birds (although these creatures were probably sick or already near death). But don’t worry, these plants pose no danger to humans, even if you fell asleep in a whole bed of them.
Just like other plants, carnivorous plants obtain energy through the process of photosynthesis, not from the meat they devour. They absorb sunlight and carbon dioxide from the atmosphere to create food (which is a simple sugar). An animal-based diet provides nutrients such as nitrogen, calcium and phosphate. These elements are used in various biological processes: protein synthesis, nucleic acid synthesis, improvement of the structure of the cell walls, etc.
Just like other plants that need to attract other creatures to help with things like pollination, carnivorous plants use different strategies to attract their prey. Carnivorous plants are often very colorful, some are sweetly scented and produce large quantities of nectar, still others have parts that are sticky or slippery or designed in a way that makes it hard for prey to escape. Once they have attracted their dinner, carnivorous plants use five basic trapping strategies or mechanisms. These five basic trapping mechanisms are: pitfall traps, fly Paper traps, snap traps, bladder traps and lobster pot traps.
Leaves of plants with pitfall traps are shaped like a funnel, and digestive enzymes are found in a pool at the bottom. After landing on the slippery edge of the leaves, the unsuspecting insect will fall into the funnel, land in the digestive juices and become trapped.
Flypaper traps use a super-glue-like substance which sticks the insects to the spot they land on and prevents them flying away. They become supper!
Snap traps are designed for the active catching of insects. After landing on the plant, the surprised insect triggers the fast closing leaves of the plant when it touches sensitive hairs which fire off the trap and the leaves, such as in the familiar Venus fly trap, quickly close and trap the prey.
Plants with bladder traps live in the water. They use a vacuum and bladder-like structure to “swallow” their prey along with the surrounding water.
Plants with lobster-pot traps use inwardly oriented hairs to force hapless insects to walk toward a pool of enzymatic juices.
The diet of almost all carnivorous plants consists of small insects and their larvae. Larger species of carnivorous plants can digest small mammals and frogs. So once they catch their prey, how do these plants digest the meal? Most carnivorous plants make their own digestive enzymes. Still others depend on bacteria to produce these enzymes; the bacteria cause the captured prey to rot, and the plant absorbs the nutrients. Still other plants rely on both their own enzymes and additional enzymes generated by bacteria. Yet another method is even more unappetizing. Some carnivorous plants use bugs and insects as helpers. For example, on carnivorous sundews, assassin bugs crawl around and eat the insects that have been captured. Then the assassin bugs poop, and the feces is used by the plant for dinner. Yuck!
Carnivorous plants can live on the ground or in the water. Most carnivorous plants are pollinated by insects attracted by beautiful and colorful flowers. The lifespan of any carnivorous plant depends of course on the species, but some such as sundews, can survive up to 50 years in the wild.
One of the most fascinating things about the group of plants is watching them move, seeing them spring their traps so incredibly quickly. The Venus fly trap has long been a favorite among kids and adults alike, we all love to see it close its leaves, trapping its dinner inside. But just how does the plant move, how is it able to snap shut? Does it have muscles? Venus fly traps aren’t the only type of carnivorous plants that move, but they are the most commonly known. What happens is this: when something touches the trigger hairs on the edges of the leaves, the cells on the inside wall of the trap transfer water to the outside walls as quick as lightning. This in turn causes the inside walls to essentially go limp. This makes the leaf snap tightly closed. Another way carnivorous plants move to entrap their food can be observed in the sundew plants I mentioned above, which have a long flypaper trap. Once the prey gets stuck on the gluey tentacles, the tentacles embrace and surround the captured creature. It does this by growing much faster on the outside than it does on the inside. The really amazing thing about this is that they can do this really, really fast. In fact one common species of sundew can bend 180 degrees in just a minute or so – wow!
Let’s take a closer look at seven of the most interesting carnivorous plants:
#7 – Utricularia
Starting the list at number seven are the Utricularia, or as they are commonly known, the bladderworts. These are a genus of carnivorous plants consisting of about 220 species. They occur in fresh water and wet soil as terrestrial or aquatic species. You find these on every continent accept Antarctica. They are the only carnivorous plants that make use of bladder traps. Most species have very small traps, in which they can catch only tiny prey, like protozoa. The traps can range from 0.2mm – 1.2cm, with the larger traps targeting larger prey like water fleas and even small tadpoles. The traps have small trigger hairs attached to a trapdoor. The bladder, when set, is under negative pressure in relationship to its surrounding area. When the trigger hairs are tripped, the trap door opens up, sucks in the insect and surrounding water, and closes the door again, all in a matter of 10 thousandths of a second! Once they prey is inside, the trapdoor closes and digestion begins.
#6 – Sarracenia
Coming in at number six are the Sarracenia, also called the North American pitcher plant. These carnivorous plants are indigenous to the eastern seaboard, Texas, the Great Lakes, and southeastern Canada, with most species being found only in the southeast United States. These are a pitfall trap plant whose leaves have evolved into a funnel, with a hood-like structure growing over the opening to prevent rain water from diluting the digestive juices. Insects are attracted by color, aroma, and a nectar-like secretion on the lip of the pitcher. Slippery footing, aided in at least one species by a narcotic drug lacing the nectar, causes insects to fall inside where they die and are digested by enzymes.
#5 – Sundews
At number five we have the sundew. Sundew is this plant’s common name, but you will also see it called by its genus name, Drosera. These plants are characterized by movable glandular tentacles, topped with sweet sticky secretions. Species from the Drosera genus are often called sundews since they, as you might imagine, appear to be covered in dew. Attracting unsuspecting insects with this “dew,” Drosera plants are able to ensnare and even digest their prey. These plants are common in nutrient-deficient places like bogs and sandy beaches. Drosera actually comprises one of the largest genera of carnivorous plants, with at least 194 species. These can be found widely spread on every continent except for Antarctica. Sundews, depending on species, can form either prostrate or upright rosettes, ranging from a half inch to a full meter in height, these beauties live for a very long time under the right conditions.
#4 – Pinguiculas
Number four would have to be the Pinguiculas. Commonly called butterworts, these plants are strikingly beautiful. They are carnivorous plants that look almost like succulents, but similar to Drosera they produce dewy, sticky leaves to capture their dinner. The leaves of the butterworts are usually bright, almost ‘electric’ green or pinkish in color. There are two special types of cells found on the top side of the butterwort leaves. One is known as a penduncular gland, and consists of secretory cells on top of a single stalk cell. These cells produce a mucilaginous secretion which forms visible droplets across the leaf’s surface, and acts like flypaper. The other cells are called sessile glands. They lie flat on the leaves surface and produce enzymes like amylase, esterase, and protease, which aid in the digestion process. There are roughly 80 species of butterwort that can be found throughout North and South America, Europe and Asia.
#3 – Nepenthes
Number three on the list are the Nepenthes. Also known as tropical pitchers or monkey cups, these somewhat larger plants are native to the more tropical regions of Sri Lanka, China, Malaysia, Indonesia, the Philippines, Madagascar, Seychelles, Australia, India, Borneo and Sumatra. There are about 130 species in all. The nickname “monkey cups” comes from the fact that monkeys have often been observed drinking rain water caught by the plants’ pitchers. These pitchers start as small buds and are filled with a self-produced liquid nectar. Lured by the nectar’s scent, insects and even small animals like mice fall into the pitcher where they find themselves trapped. When the plant senses motion in this pitcher, its digestive processes begin. Nepenthes secrete powerful digestive juices that can break down their prey, allowing the plants to gain the nutrients they need for survival. Most species of Nepenthes are tall creepers (10-15m), with a shallow root system. From the stem you will often see sword-like leaves growing, with a tendril (often used for climbing) protruding from the tip of the leaf. At the end of the tendril, the pitcher forms first as a small bulb, which then expands and forms a cup.
#2 – Byblis
Number two on our list of carnivorous lovelies is the Byblis, or rainbow plant. This is a small genus of carnivorous plants native to Australia. The name rainbow plant comes from the attractive appearance of their mucilage-covered leaves in the sun. Even though these plants look similar to the Drosera and Drosophyllum, they are not related in any way and can be distinguished by zygomorphic flowers with five curved stamens. The leaves have a round cross section, and they tend to be very elongated and tapered at the end. The surface of the leaves are completely covered in glandular hairs that release a sticky mucilaginous substance, which in turn traps small insects on the leaves or tentacles as a passive fly paper trap.
#1 – Venus Fly Trap
Number one, of course, is the very famous Venus fly trap, Dionaea muscipula. Let’s face it, when most people think of carnivorous plants, Venus fly traps are the plant that comes to mind first. The Venus fly trap is known for its hinged, leafy “jaw” that snaps together to trap and consume unsuspecting insects. This famous fellow is a rather small plant that has four to seven leaves growing from a short subterranean stem. The leaf blade is divided into two regions: a flat, long, heart-shaped, photosynthesis-capable petiole, and a pair of terminal lobes, hinged at the midrib, forming the trap which is actually the true leaf. The inner surfaces of these lobes contain a red pigment and the edges secrete mucilage. When an insect, beetle, or frog touches two or more of the plant’s “hairs,” the flytrap quickly hinges shut, trapping and then slowly digesting the prey. Venus fly traps are one of the few plants that can perform rapid movements. When the fly trap has fully digested an insect, it opens up its jaw once more, ready for its next meal. To prevent wasting energy on trapping inanimate objects like raindrops, the jaw will only close after two or more hairs are touched within about 20 seconds of the first movement. The hinged lobes snap shut in about 0.1 seconds. Man – that is fast! They are fringed by stiff, thorn-like protrusions called cilia, which mesh together and prevent the prey from escaping. When the dinner guest is unable to escape and the inner surfaces of the lobes are continuously being stimulated, the edges of the lobes grow or fuse together, sealing the trap and creating an enclosed “stomach” in which digestion and absorption can take place.
I first fell in love with carnivorous plants back in the fourth or fifth grade, when a teacher named Mrs. Kuttla brought in a Venus fly trap as a class pet. For some unknown reason, we called the plant Luke. I would spend any time I could watching Luke, and I loved it when I would see him snap shut on an ant or a spider. The most fun of all was when I got to feed him raw hamburger! As a kid, I just loved that plant. And believe me, with a class of 30 kids to feed him, Luke never went hungry!
Luke was lucky that all of us kids had plenty of food to eat from the school cafeteria, so eating him never crossed our minds. But as we grew up and left school, we all started to make our own decisions about our diets. Some of us continued to eat meat regularly, but a few of us became vegetarians. Now I wonder, if we could go back in time, would a vegetarian eat that carnivorous plant? I guess I’ll never know. If you’re a vegetarian – tell me what you think in the comments section below. Would you eat Luke?