The Venus Flytrap: A Vulnerable and Carnivorous Plant
A Fascinating and Vulnerable Plant
The Venus flytrap is an intriguing plant that is in trouble in the wild. Like other plants, it has chloroplasts and makes food via photosynthesis. It also traps and digests insects to supplement the low concentration of nitrogen in its boggy habitat. The plant's ability to lure its prey into its trap and the rapid closure of the trap doors are fascinating for many people. The appearance of the empty husk of an insect when the trap opens up is impressive evidence of the plant's digestive power.
Wild Venus flytraps are found only in North Carolina and South Carolina in the United States. The population is currently classified as vulnerable and is facing some serious stresses. In October 2016, botanists from the University of Wisconsin-Madison announced that they had filed an emergency petition with the U.S. Fish and Wildlife Service. The petition asked for the Venus Flytrap to be classified as endangered.
The scientific name of the Venus flytrap is Dionaea muscipula. It belongs to the flowering plant family known as the Droseraceae. The flytrap and one other species (the waterwheel plant) are sometimes referred to as snap traps due to their method of catching prey.
Leaves and Traps
The leaves of the Venus flytrap are highly specialized. They grow in a rosette that is produced by an underground stem known as a rhizome. The first section of each leaf is flattened. It has a narrow base and gradually widens towards its tip. At the widest point is a short stalk that attaches the trap to the rest of the leaf.
The trap consists of two lobes with a hinge between them. The hinge allows the lobes to come together as the trap closes. The edges of the lobes have long spikes that keep the prey captive. The trap is green on the outside and deep red, pale red or green on the inside. The overall effect is reminiscent of an animal's jaw and teeth.
Flowers and Fruit
The flowers of the Venus flytrap have a green centre and white petals decorated with green lines. They are pollinated by insects. The flowers are borne on tall stalks that extend far beyond the leaves. This prevents pollinating insects from being trapped by the plant.
The fruit is a green pod that is roughly rounded in shape instead of being shaped like a pea pod. The pod opens to reveal shiny black seeds. Each seed is rounded at one end and pointed at the other.
The plant is named after Venus, the Ancient Roman goddess of love and beauty. The name may have arisen due to the beauty of the flowers.
Trapping and Digesting Prey
The trap secretes a sweet nectar that attracts prey. The prey animal is generally an insect but may be a spider. There are four trigger hairs on the interior surface of each lobe. The trap doesn't close the first time that a trigger hair is stimulated by the prey. If there is another hair stimulation within about twenty seconds, however, the trap is sprung. It sometimes closes in as little as a tenth of a second.
The trap doesn't close completely at first, which allows smaller prey to escape. This behaviour may have developed because it prevented the plant from digesting prey that supplied little nutrition. The trap soon becomes an impenetrable chamber, sealing the fate of its victim.
In contrast to the rapid capture of the prey, digestion is a lengthy process that takes about five to ten days. The products of digestion are absorbed and used. The plant is unable to digest the tough outer layer of an insect, which is known as an exoskeleton. When the trap opens, the exoskeleton is blown away by wind or washed away by rain. The trap is then ready to capture prey again. After three or four captures, the trap (but not the plant) dies.
Venus Flytraps Catching Their Prey
How Do the Traps Close?
Unlike humans, the Venus flytrap doesn't have nerves to transmit electrical signals or a brain to respond to them. Nevertheless, electrical signals are generated in a stimulated trap and travel along the surface of cells. In addition, the plant responds appropriately to the signals, even though it doesn't have muscles.
The full details of trap action are unknown, but some interesting facts have been discovered. According to a research team led by Dr. Ranier Hedrich at the University of Würzburg, one touch to the trigger hairs elicits no response. This is advantageous for the plant, since it reduces the chance that it will respond to debris or water drops that land on the open trap. A second touch within fifteen to twenty seconds creates an electrical impulse known as an action potential. This impulse causes a large amount of water to enter the cells in the trap, which changes their shape. As a result, the trap closes.
Jasmonic Acid and Digestive Enzymes
After a trap has closed, the plant continues to "count" and respond to trigger hair stimulation. A third touch to the hairs causes the trap to produce a hormone called jasmonic acid. The hormone triggers the digestive glands in the trap to make enzymes. Subsequent touches to the hairs cause digestive enzymes to be released from the glands. The enzymes break down the tissues of the prey, providing nutrition for the plant.
Jasmonic acid is also found in many plants that aren't carnivorous. Here it stimulates the production of enzymes that destroy insect pests. It's interesting that the hormone serves related functions in different types of plants.
The studies of trap action indicate that in essence the Venus flytrap counts and remembers. It doesn't perform these actions consciously, however.
In the wild, the Venus flytrap is found only in the southeastern part of North Carolina and the northeastern part of South Carolina. Its population is decreasing due to development and poaching. The bogs where the plants grow are being drained and covered to create land for humans. Another problem is that some people collect large numbers of plants to sell.
The Venus flytrap is unlikely to become extinct in the near future due to its cultivated population. Researchers say that they are currently more plants in homes and gardens than in the wild. There are drawbacks to the existence of a species only in captivity, however.
It's sad when the biodiversity of the planet is decreased. There may be practical problems with loss of biodiversity as well as emotional ones. If a plant exists only in a cultivated form, its natural evolution is disturbed and is replaced by selective breeding by humans. Scientists are discovering that plants in nature often have beneficial characteristics for humans. The potential benefits of a plant may be lost in captivity.
Snaptraps have only evolved once in the 3.7 billion-year history of life on Earth. This species is native to just one area of North America, and represents a unique and fascinating offshoot in the tree of life.— Don Waller, UW-Maddison
How to Care for a Venus Flytrap
A Venus flytrap is a fascinating plant for people to have in a home, especially for children. It's important to buy a flytrap from a reputable nursery that sells only cultivated plants. This will help to protect the wild population. Another advantage is that nursery staff will probably be able to offer advice about keeping the plant alive and healthy. The plant is a perennial and requires moist, acidic soil that mimics the substrate found in its natural habitat. It also requires a periodic meal of a live insect.
Flytraps take a long time to grow from seeds, so cultivated plants are usually produced by other methods. Division of a plant at suitable times of the year is sometimes used to produce new individuals. The plants are also generated by a process known as tissue culture. This involves the stimulation of a small piece of plant tissue in a lab. The tissue is supplied with nutrients and treated with hormones that stimulate root and shoot growth.
Cultivated plants are interesting and often enhance our lives. Wild populations are also important, however. As the scientist in the quote above says, snap traps (or snaptraps) have evolved only once on Earth. The Venus flytrap is a unique plant. It would be a great shame to lose it from the wild.
© 2016 Linda Crampton