Venus Flytrap

Venus Flytrap
Venus Flytrap leaf
Conservation status

Vulnerable (IUCN 2.3)[1]
Scientific classification
Kingdom: Plantae
(unranked): Angiosperms
(unranked): Eudicots
(unranked): Core eudicots
Order: Caryophyllales
Family: Droseraceae
Genus: Dionaea
Species: D. muscipula
Binomial name
Dionaea muscipula
Sol. ex J.Ellis
Venus Flytrap distribution
Synonyms
  • Dionaea corymbosa
    (Raf.) Steud. (1840)
  • Dionaea crinita
    Sol. (1990) nom.superfl.
  • Dionaea dentata
    D'Amato (1998) nom.nud.
  • Dionaea heterodoxa
    D'Amato (1998) nom.nud.
  • Dionaea muscicapa
    St.Hil. (1824) sphalm.typogr.
  • Dionaea sensitiva
    Salisb. (1796)
  • Dionaea sessiliflora
    (auct. non G.Don: Raf.) Steud. (1840)
  • Dionaea uniflora
    (auct. non Willd.: Raf.) Steud. (1840)
  • Drosera corymbosa
    Raf. (1833)
  • Drosera sessiliflora
    auct. non G.Don: Raf. (1833)
  • Drosera uniflora
    auct. non Willd.: Raf. (1833)

The Venus Flytrap, Dionaea muscipula, is a carnivorous plant that catches and digests animal prey—mostly insects and arachnids. Its trapping structure is formed by the terminal portion of each of the plant's leaves and is triggered by tiny hairs on their inner surfaces. When an insect or spider crawling along the leaves contacts a hair, the trap closes if a different hair is contacted within twenty seconds of the first strike. The requirement of redundant triggering in this mechanism serves as a safeguard against a waste of energy in trapping objects with no nutritional value.

The plant's common name refers to Venus, the Roman goddess of love, whereas the genus name refers to Dione.[2] Dionaea is a monotypic genus closely related to the waterwheel plant and sundews.

Contents

Description

The Venus Flytrap is a small plant whose structure can be described as a rosette of four to seven leaves, which arise from a short subterranean stem that is actually a bulb-like object. Each stem reaches a maximum size of about three to ten centimeters, depending on the time of year;[3] longer leaves with robust traps are usually formed after flowering. Flytraps that have more than 7 leaves are colonies formed by rosettes that have divided beneath the ground.

Illustration of the Venus Flytrap from Curtis's Botanical Magazine.

The leaf blade is divided into two regions: a flat, heart-shaped photosynthesis-capable petiole, and a pair of terminal lobes hinged at the midrib, forming the trap which is the true leaf. The upper surface of these lobes contains red anthocyanin pigments and its edges secrete mucilage. The lobes exhibit rapid plant movements, snapping shut when stimulated by prey. The trapping mechanism is tripped when prey contacts one of the three hair-like trichomes that are found on the upper surface of each of the lobes. The trapping mechanism is so specialized that it can distinguish between living prey and non-prey stimuli such as falling raindrops;[4] two trigger hairs must be touched in succession within 20 seconds of each other or one hair touched twice in rapid succession,[4] whereupon the lobes of the trap will snap shut in about 0.1 seconds.[5] The edges of the lobes are fringed by stiff hair-like protrusions or cilia, which mesh together and prevent large prey from escaping. (These protrusions, and the trigger hairs, also known as sensitive hairs, are probably homologous with the tentacles found in this plant’s close relatives, the sundews.) Scientists are currently unsure about the evolutionary history of the Venus flytrap; however scientists have made hypotheses that the flytrap evolved from Drosera (sundews).[6]

The holes in the meshwork allow small prey to escape, presumably because the benefit that would be obtained from them would be less than the cost of digesting them. If the prey is too small and escapes, the trap will reopen within 12 hours. If the prey moves around in the trap, it tightens and digestion begins more quickly.

Speed of closing can vary depending on the amount of humidity, light, size of prey, and general growing conditions. The speed with which traps close can be used as an indicator of a plant's general health. Venus Flytraps are not as humidity-dependent as are some other carnivorous plants, such as Nepenthes, Cephalotus, most Heliamphora, and some Drosera.

The Venus Flytrap exhibits variations in petiole shape and length and whether the leaf lies flat on the ground or extends up at an angle of about 40-60 degrees. The four major forms are: 'typica', the most common, with broad decumbent petioles; 'erecta', with leaves at a 45 degree angle; 'linearis', with narrow petioles and leaves at 45 degrees; and 'filiformis', with extremely narrow or linear petioles. Except for 'filiformis', all of these can be stages in leaf production of any plant depending on season (decumbent in summer versus short versus semi-erect in spring), length of photoperiod (long petioles in spring versus short in summer), and intensity of light (wide petioles in low light intensity versus narrow in brighter light).

When grown from seed, plants take around four to five years to reach maturity and will live for 20 to 30 years if cultivated in the right conditions.[7]

Mechanism of trapping

Closeup of one of the hinged trigger hairs.
A closing trap.
Closed cilia around the prey

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,[5] 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.[8] 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.[9][10]

Digestion in Dionaea muscipula

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 catalysed 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.[11] Such oxidative modification could rupture animal cell membranes. Plumbagin is known to induce apoptosis, associated with the regulation of Bcl-2 family of proteins.[12] When the Dionaea extracts were preincubated with diaphorases and NADH in the presence of serum albumin (SA), subsequent tryptic digestion of SA was facilitated.[11] 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.[11]

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.

Habitat

The Venus Flytrap is found in nitrogen-poor environments, such as bogs and wet savannahs. Small in stature and slow growing, the Venus flytrap tolerates fire well, and depends on periodic burning to suppress its competition.[13] Fire suppression threatens its future in the wild.[14] It survives in wet sandy and peaty soils. Although it has been successfully transplanted and grown in many locales around the world, it is found natively only in North and South Carolina in the United States, specifically within a 60 mile radius of Wilmington, North Carolina. [15] One such place is North Carolina's Green Swamp. There also appears to be a naturalized population of Venus Flytraps in northern Florida as well as populations in the New Jersey Pine Barrens. The nutritional poverty of the soil is the reason that the plant relies on such elaborate traps: insect prey provide the nitrogen for protein formation that the soil cannot. The Venus Flytrap is not a tropical plant and can tolerate mild winters. In fact, Venus Flytraps that do not go through a period of winter dormancy will weaken and die after a period of time.[16]

Cultivation

Time-lapse photography of a growing trap.
The 'Dentate' cultivar of the venus fly trap in cultivation
Healthy venus flytraps produce flowers in the spring
Seeds
Typical variety of the Venus Flytrap.
Dionaea muscipula 'Akai Ryu', Japanese for 'Red Dragon', in cultivation.

Venus flytraps are popular as cultivated plants, but have a reputation for being difficult to grow.[3] Successfully growing these specialized plants requires recreating a close approximation to the plant's natural habitat.

Healthy Venus flytraps will produce scapes of white flowers in spring, however, many growers remove the flowering stem early (2-3 inches), as flowering consumes some of the plant's energy, and reduces the rate of trap production. If healthy plants are allowed to flower, successful pollination will result in the production of dozens of small, shiny black seeds.

Plants can be propagated by seed, although seedlings take several years to mature. More commonly, they are propagated by division in spring or summer.

Cultivars

Venus flytraps are, by far, the most commonly recognized and cultivated carnivorous plant. They are sold as houseplants and are often found at florists, hardware stores and supermarkets. During the past ten years or so large quantities of cultivars have come into the market through tissue culture of select genetic mutations. It is through tissue culture that great quantities of plants are raised for commercial markets.

The registered cultivars (cultivated varieties) include (name of originator in brackets):

An unofficial list includes many more names, with more added annually. None of these "variation names" are officially recognized unless the name is properly documented, registered and accepted by the International Registration Authority for carnivorous plant cultivars, the International Carnivorous Plant Society.

Conservation

The general consensus of most professional plant conservationists is that the best means to ensure survival of the Venus Flytrap is to protect a number of populations in their native and natural habitats, preferably as large areas of managed preserves. Although it may be possible to perpetuate the species indefinitely in cultivation, this is no substitute for protecting wild populations in their natural habitats. For example, cultivation by its very nature exerts strong artificial selection pressures that will change the species, possibly in unintended or unexpected ways. Such ex-situ conservation is severely limited also because plants become diseased or eaten and because there are unavoidable random events ranging from the greenhouse heat failing in winter to full scale wars. In essence, the safest place for the Venus flytrap is in nature. The natural beauty of the wild populations of flytraps has been marred by decades of field-collection by and for plant collectors and has taken a heavy toll. Many wet pine savannas, once inhabited by thousands of flytraps, are now pock-marked with holes where plants were dug for sale. Many of these plants end up on window sills as novelty items that die in a few short weeks or months.

Efforts should be made most vigorously, therefore, to preserve wild populations. Conservation of the flytrap means buying up and protecting lands on which it naturally grows, which then can be preserved, managed, and restored. This effort costs considerable money. One solution to the problem is to place a surcharge on each plant sold to generate funds to save wild populations.

Currently, there are estimated to be more than 3-6 million plants in cultivation compared to only 35,800 plants remaining in nature.[17] Several prominent plant conservationists suggest the plant be labeled as Vulnerable.[17] Precise data on the distribution of population sizes in 1992 from the Office of Plant Protection suggests a more dire state for the species. Every size class in red is slated for eventual extinction with the green ones persisting longer. In essence, all smaller populations may go extinct for stochastic reasons and, since small population are more numerous in nature now and contribute more to the total number of plants remaining in the species, most of this unique and remarkable carnivorous plant species may be going extinct soon. Note that the figure of 35,800 plants in 1992 is over 15 years old and undoubtedly, therefore, underestimates the current situation.

References

  1. ↑ Schnell, D., Catling, P., Folkerts, G., Frost, C., Gardner, R., et al. (2000). Dionaea muscipula. 2006. IUCN Red List of Threatened Species. IUCN 2006. www.iucnredlist.org. Retrieved on 11 May 2006. Listed as Vulnerable (VU A1acd, B1+2c v2.3)
  2. ↑ "Dionaea". Genus name origin. http://dictionary.reference.com/browse/dionaea. Retrieved 2009-05-28. 
  3. ↑ 3.0 3.1 "Venus Flytraps". The Carnivorous Plant FAQ. http://www.sarracenia.com/faq/faq2000.html. Retrieved 2005-06-13. 
  4. ↑ 4.0 4.1 Raven, Peter H.; Evert, Ray Franklin; Eichhorn, Susan E. (2005). Biology of Plants (7th ed.). W.H. Freeman and Company. ISBN 0716710072. 
  5. ↑ 5.0 5.1 Forterre, Yoël; Skotheim, Jan M.; Dumais, Jacques; Mahadevan, L. (27 January 2005). "How the Venus flytrap snaps" (pdf). Nature 433: 421–425. doi:10.1038/nature03185. http://www.oeb.harvard.edu/faculty/dumais/Publications/Nature2005.pdf. 
  6. ↑ Cameron, Kenneth M.; Wurdack, Kenneth J.; Jobson, Richard W. (2002). "Molecular evidence for the common origin of snap-traps among carnivorous plants". American Journal of Botany 89 (9): 1503–1509. doi:10.3732/ajb.89.9.1503. http://www.amjbot.org/cgi/content/abstract/89/9/1503. 
  7. ↑ D'Amato, Peter (1998). The Savage Garden. Berkeley, California: Ten Speed Press. ISBN 0898159156. 
  8. ↑ Hodick, Dieter; Sievers, Andreas (1989). "The action potential of Dionaea muscipula Ellis". Planta 174 (1): 8–18. doi:10.1007/BF00394867. http://www.springerlink.com/index/KL80VV1327508844.pdf. 
  9. ↑ Williams, S. E. 2002. Comparative physiology of the Droseraceae sensu stricto—How do tentacles bend and traps close? Proceedings of the 4th International Carnivorous Plant Society Conference. Tokyo, Japan. pp. 77-81.
  10. ↑ Hodick, Dieter; Sievers, Andreas (1988). "On the mechanism of closure of Venus Flytrap (Dionaea muscipula Ellis)". Planta 179 (1): 32–42. doi:10.1007/BF00395768. http://www.springerlink.com/index/QPK061437U675H10.pdf. 
  11. ↑ 11.0 11.1 11.2 Galek H, Osswald WF, Elstner EF (1990). "Oxidative protein modification as predigestive mechanism of the carnivorous plant Dionaea muscipula: an hypothesis based on in vitro experiments". Free Radic Biol Med. 9 (5): 427–34. doi:10.1016/0891-5849(90)90020-J. PMID 2292436. 
  12. ↑ Hsu YL, Cho CY, Kuo PL, Huang YT, Lin CC (Aug 2006). "Plumbagin (5-Hydroxy-2-methyl-1,4-naphthoquinone) Induces Apoptosis and Cell Cycle Arrest in A549 Cells through p53 Accumulation via c-Jun NH2-Terminal Kinase-Mediated Phosphorylation at Serine 15 in Vitro and in Vivo". J Pharmacol Exp Ther. 318 (2): 484–94. doi:10.1124/jpet.105.098863. PMID 16632641. 
  13. ↑ W. Schulze, E.D. Schulze, I. Schulze, and R. Oren (2001). "Quantification of insect nitrogen utilization by the venus fly trap Dionaea muscipula catching prey with highly variable isotope signatures". Journal of Experimental Botany 52 (358): 1041–1049. doi:10.1093/jexbot/52.358.1041. PMID 11432920. http://jxb.oxfordjournals.org/cgi/content/full/52/358/1041. 
  14. ↑ Leege, Lissa. "How does the Venus flytrap digest flies?". Scientific American. http://www.sciam.com/article.cfm?id=how-does-the-venus-flytra. Retrieved 2008-08-20. 
  15. ↑ Darwin, C. R. 1875. Insectivorous Plants.
  16. ↑ www.carnivorousplants.org
  17. ↑ 17.0 17.1 How to generate funds to conserve wild populations

External links

Carnivorous plants (list)
Genera
Aldrovanda • Brocchinia • Byblis • Catopsis • Cephalotus • Darlingtonia • Dionaea • Drosera • Drosophyllum • Genlisea • Heliamphora • Nepenthes • Philcoxia • Pinguicula • Roridula • Sarracenia • Triphyophyllum • Utricularia
Protocarnivorous
Aracamunia • Capsella • Colura • Dipsacus • Drymocallis • Geranium • Ibicella • Paepalanthus • Passiflora • Plumbago • Proboscidea • Stylidium
Extinct
Archaeamphora • Droserapites • Droserapollis • Droseridites • Fischeripollis • Palaeoaldrovanda • Saxonipollis
See also
International Carnivorous Plant Society • Insectivorous Plant Society • Pitcher plant