Nature Study # 232: Venus Fly Trap
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The Venus Fly Trap, Dionaea muscipula (meaning Dionaea's, or Aphrodite, the daughter of Dione, Mousetrap), is a carnivorous plant native only to a small area of the US, the sandy bogs and swamplands of North and South Carolina. These regions have very nutrient-poor soil, making plant life difficult and so they catch flies to supplement their diets with extra nitrogen. Because of this, they have unique needs for their care. They need as much light as you can give them. Direct bright sunlight at least four hours a day is best. Too many chemicals or even nutrients (that are usually good for plants) will kill them. For this reason, water them with pure water, either distilled, rain water and do not give them plant food. Plant them in a nutrient poor medium such as peat, sphagnum moss, sand or perlite, or some combination. They are perennial plants and so they grow and bloom over the spring and summer and then die back every winter, growing back in the spring from their energy reserves saved up in the rhizome or root-stock. They can withstand frost and light freezes but not freezes that last an extended period of time. They propagate by two methods, by seed from the flower as through the rhizome, which are runners that start new plants wherever they take root.
It preys on insects with its unique leaves. The leaves have a broad flat typical leaf-like region called the leaf-base that is capable of carrying out photosynthesis and grows out of the ground, and the trapping mechanism, the leaf-blade, at the end of the leaf that is composed of two lobes with hinged together by a midrib. Each trap usually has between two and five "trigger" hairs on each lobe. The edge of the trap is lined with teeth or finger-like cilia that lace together when the trap shuts. The leaf-base and leaf-blade are joined together by the petiole. On the upper portion of each side of the trap the Venus Fly Trap there are anthocyanins, which are little pigments that appear red or purple on the surface of the trap. This coloration is helps to draw in insects, as does a type of protein, mucilage, a sweet smelling nectar, that the trap secretes. Once the insect has landed on the leaf, it begins to crawl around on the leaf surface lapping up the mucilage, inadvertently touching the trigger hairs on the leaf, causing the trap to snap shut.
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If the initial snap of the trap is successful in capturing prey, then the trap will begin the tightening phase, which usually causes the struggling prey inside the to touch the trigger hairs, giving the plant the signal to continue to tighten its hold on the victim. On the other hand, if the prey is small enough, it can slip through the teeth of the trap and escape. If the trap is unsuccessful in capturing any prey when it closes because the prey was able to escape or it was trigger to close by a leaf, a couple drops of rain, or by a person sticking a finger or stick into the trap, the tightening phase will not occur. The trap will slowly begin to reopen and should be fully open again within a day or two. However, if the trap is triggered to close many time, it will eventually turn black and die, which is the reason it is not suggested that the trap be triggered by a pencil or other source, just to see the leaves close. If the plant has been successful in trapping an insect and the tightening phase has occurred, the rims of the lobes just underneath the teeth on either side of the trap are pushed tightly together. Once the seal is tight, the digestive enzymes are released, drowning the insect and beginning the digestion process. For the next five to 12 days, the trap will remain closed while it performs digestion. During this time it will continue to secrete digestive enzymes that will dissolve the soft tissues of the insect releasing the nutrients contained within it so that they can be absorbed into the leaf. After the digestion of the meal is finished, the leaf will reabsorb the digestive fluid. This signals the plant to reopen the trap. What is left is the exoskeleton of the digested insect. This is either washed out by rain, blown out by wind, or serves as a lure for the trap's next victim. Often spiders and ants are lured in by the dead insect and end up as a second meal for the trap. After several captures, the trap will stop working, turn black and drop off. The plant can can be fed hand-fed, but the plant should not be fed more than once a week. You must feed it freshly killed (or live) insects and not people food, like hamburger. If the plant does not get any insects at all, it may survive but it will not grow very well.
Flytraps will typical grow beautiful white flowers on a long stalk, about 6 inches above the traps so that pollinating insects are not as easily devoured by the plant. Making a flower takes a lot of energy, and the traps of a flowering plant go through a period in which their development is slowed.
Leading Thought:
The Venus Fly Trap is among the most fascinating of plants, the carnivorous plants. It is worth the time to study the unique needs of this unusual plant type.
Method:
It is best to have the plant in the classroom so that the pupils can observe first hand the most fascinating way this plant gets the nutrients it needs, and the parts that this plant has in order to get its needs met.
Observations for Pupils:
1. Why do you suppose this plant has the name "Venus Flytrap"? Who was Venus in Greek mythology? Why would the plant's name include this Goddess? How can looking at its name give us clues to understanding the unique nature of this plant?
2. The plant grows naturally only in the sandy bogs and swamplands of North and South Carolina, a region that has very nutrient-poor soil. Can you make any speculations as to why the Venus Flytrap catches flies, given this?
2. Observe the unusual leaves of the Venus Flytrap. Why does it have a colorful inside? Can you speculate why the leaves have tiny hairs in them?
3. Catch or kill a insect small enough to fit in the Flytrap's leaves. Put it on the very tip of a toothpick and hold it inside the lobes of the leaf, making sure to rub it against the hairs. When the lobes close, slip the toothpick out and watch the tightening phase. Record any observations.
4. Sketch the flytrap and label its parts. Label the trap (the part that catches the insect) "Two-Lobed Blade." Each half of the trap is a a leaf blade or lobe. Label the trap's teeth (the spikes at the edges of the lobes) "Cilia." The cilia interlace when the trap snaps shut. Label the hairs inside the trap "Trigger Hairs." Label the flat stalk below the trap "Petiole." This part of the Venus flytrap plant connects the two parts of the Venus flytrap leaf: the lower leaf and the two-lobed blade trap.Label a leaf at the base of the Venus flytrap "Leaf," or, to refer to the base of the plant, "Leaf Base." The lower leaves nourish the plant via photosynthesis the same way regular plants do.Label the part of the Venus flytrap below the growing medium "Rhizome." The rhizome is a bulb-like structure at the base of the plant. Label the area below the rhizome "Roots." The Venus flytrap has small roots.(This information come from the following website. If you want to read more:
5.Catch or kill a insect small enough to fit in the Flytrap's leaves. Put it on the very tip of a toothpick and hold it inside the lobes of the leaf, making sure to rub it against the hairs. When the lobes close, slip the toothpick out and watch the tightening phase. Record any observations.
6. Keep track of what leaves have closed for any length of time.(You can make a graph of this, if you like.) Do you see any leaves that are beginning to turn brown and drop off. Can you speculate why this might be. Have you noticed any correlation between how often they have closed and their turning brown. Due to your observations, can you make a speculations as to how often the plant catches insects before it turns brown and drops off?
7. It may also be fitting to complete at this time Lesson 170: The Strawberry in the Handbook of Nature Study, which is also a plant which reproduces both with seed and rhizome.
(Note: This is my first attempt to write in the style of Anna Botsford Comstock. I, by no means, think that I am as talented and knowledgeable as she was in biology or nature study, but I only serve to emulate her through imitation, as clumsy as it may seem. I hope that you enjoy my efforts.)
