Some Plants Have Sneaky Plans
I remember one beautiful summer day when our family decided to hike in a local wetland (marsh). As they scampered along, the children were very taken by yellow snapdragon-like flowers projecting above the water surface. Was this somebody’s idea of a joke? Who planted garden flowers under water? This plant however is anything but humorous. Its purpose is to trap and digest small aquatic organisms like water fleas, mosquito wrigglers, tiny worms or anything that is the right size and moves.
Upon hearing about this plant, the children’s attitude was “How weird is that?” Everybody knows that animals move and plants don’t.
How can aquatic creatures be so stupid as to let themselves be caught by a plant? The victims however aren’t stupid, they are just outsmarted by the plant’s design. Firstly, the plant which is suspended under the surface of the water, secretes compounds which attract victims. These plants feature innocent-looking little egg-shaped bladders connected to the plant stem. When a victim like a water flea brushes against a trigger hair on a bladder, a cascade of events follows which ends in disaster for the intruder.
A trapdoor in the bladder wall swings up and inward. Water rushes in to fill a vacuum in
the interior cavity. The inward tide carries the victim along. The trapdoor swings firmly shut
behind the creature and its struggles stimulate the release of special enzymes which digest the
victim. Once the products of animal digestion have been absorbed by the plant, the trap is re-
set. Special glands absorb the water from the interior, restoring a vacuum, so that the trap is
ready for another victim.
This ingenious plant is called bladderwort or Utricularia. Of the 200 or so species known
worldwide, about 20 occur in North America and only 3 in Alberta. Bladderwort is one of the
more amazing designs in a group of plants that enhance their lifestyles by digesting animals.
The provincial flower of Newfoundland (Sarracenia purpurea) is another carnivorous plant. This
plant grows mainly in boggy areas of the northern boreal forest. The traps consist of a rosette of leaves which stand somewhat upright. The shape of the leaves is like narrow hollow cones,
open at the top with a specially decorated hood at the top that stands vertically. The hood is
covered in stiff downward pointing hairs which encourage an insect or small lizard to move
downward toward the cavity which is filled with rainwater and digestive enzymes. The
downward pointing hairs mean that it is extremely difficult to crawl upward to escape the fatal
Carnivorous plants occur worldwide, especially in habitats which offer soil with low
nutrients. Australia is famous for its variety of these plants since the soil there is so lacking in
nitrates and phosphates. Nevertheless, the most famous carnivorous plant is the Venus flytrap
(Dionaea ), found only in a restricted area near the American Atlantic coast of North and South
Carolina. This plant specializes in catching large walking or jumping insects and spiders.
The Venus flytrap plant is only a few inches tall and consists of 4-7 leaves arranged in a
rosette. All the traps are modified leaves or parts of leaves. Each trap consists of hinged half
leaves lying face side up. These halves are able to snap together like a mollusk bivalve shell.
(Think clam.) The trap surface is armed with hairs sensitive to touch. To stimulate a response,
however, there have to be two touches within 20 seconds (which means that a living creature
and not a falling object is involved). Once stimulated, an electrical impulse triggers the hinged
leaves to snap closed within ‘nanoseconds’. The electrical signal is much like our own nervous
There follows a cascade of events that all mean doom for the trapped victim. Digestive
enzymes are pumped into the cavity between the leaf halves and later other enzymes facilitate
the moving of these new nutrients into the leaf. An article in Smithsonian Magazine March 9,
2022 declared: “Evolution has co-opted root genes and put them to work in the leaf. In roots,
transporter genes are always active, but in the leaf only once nutrients are available.”
The Smithsonian article claims that the carnivorous lifestyle in plants arose independently at least twelve times through evolution, a “classic case of convergent evolution.” The term convergence means some different creatures converged on the same obscure choice for unknown reasons by unknown processes. This is an attempt to explain why some diverse organisms exhibit features in common which cannot be explained by their having developed from a common ancestor. This idea of convergence is an attempt to rescue evolution from its failure to explain an observation such as the situation we see with the carnivorous plants. [see Convergence in HeadStart]
The popular explanation about where carnivorous plants come from, however, mainly
involves co-option, another attempt to rescue evolutionary explanations. “Co-option is an
attempt to avoid the difficulties of explaining how natural selection could select for traits, the
component parts of which must be fully assembled before they are functional.” [see Co-option
in HeadStart] The Smithsonian article reports that recent findings point to co-option and re-
purposing existing genes. Although the evolutionary process is supposed to be blind, with no
objective or purpose, nevertheless the article in Smithsonian Magazine declares: “Evolution is
sneaky and flexible. It’s simpler in evolution to repurpose something than to make something
new.” This sounds as if the evolutionary process has an objective!Another author, discussing evolutionary co-option, declared: “The only difference between human and evolutionary co-option is that we purposefully change an object’s function, while evolution simply takes advantage of an opportunity with no direction, purpose, or forethought.” [Deborah McLennan. 2008. Evo Edu Outreach quoted in HeadStart]. One wonders how a process can be successful when it is so directionless.
Evolution may be blind, but scientists since the 1970s have discovered some eerie similarities among carnivorous plants. Most ordinary plants employ some enzymes to attack invading disease agents or animals that want to eat the plant. The enzymes that carnivorous plants use to digest their victims, seem similar to the defensive enzymes. The eerie observation however is that: “In many cases [carnivorous] plants that evolved entirely independently, used the same genes.” [Smithsonian Magazine] Even more surprising, the DNA sequences for the digestive enzymes in all these carnivorous plants, are almost the same. How does a blind process find the exact most suitable starter genes, not once but many times? And how does that blind process just happen to modify these genes in the exact same way? Evolution fails as an explanation. Carnivorous plants are not the product of evolution, but of intelligent choice. These plants were designed to survive in nutrient-poor conditions and they do this with flair and panache. They are not only diverse, but beautiful and interesting.
Did we communicate all this to the children in the marsh on that summer day? Maybe we should run over that discussion with them again! Is anyone up for a hike? Acid bogs, for their part, offer a variety of other carnivorous species. Sundew and butterwort are common in Alberta. They catch insects by the simple expedient of sticky drops on their leaves, but they still have to digest their victims and absorb the nutrients. Let’s go!
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