Beware! Hungry Plants Await Their Meal

William Sutherland
 


Visitors: 260

Generally plants gain nutrition through their roots (water and minerals) and leaves (absorption of sunlight and carbon dioxide (CO2)) to create ATP ((adenosine triphosphate or energy) to meet their metabolic needs) and starch (a reserve for when photosynthetic conditions are not optimal (e. g. reduction in intensity and length of sunlight, droughts, frosts, and other adverse situations). However, carnivorous/“insectivorous” plants must ingest additional sources of food. Accordingly they “attract, capture, kill, digest, and absorb [the enzymes of living] prey”[1] consisting mainly of invertebrates.

Currently there are 600+ known species of carnivorous plants belonging to at least nine plant families that use a variety of methods to lure and trap prey – sweet scents, chemical secretions, colorful flowers and/or orbs, slippery or sticky surfaces and/or mechanical traps. Although they generally grow in temperate places “where water and seasonal sunshine are abundant and the soil is [acidic] and poor in nutrients (especially nitrates, calcium, phosphates, and irons, which are essential for protein synthesis, cell wall stiffening, nucleic acid synthesis, and chrolophyll synthesis, respectively) such as acidic bogs, [fens] and rock outcroppings, ” [2] they exist in many areas. They live on land and in water (e. g. the venus flytrap (Dionaea muscipula) lives in acidic compounds consisting of high concentrations of ammonium (a toxic substance) with a pH of between 4 to 5, while the bladderwort (Utricularia genus) lives in water). Some grow out of moist boggy compounds (e. g. pitcher plants – Darlingtonia and Sarracenia), some grow in non-temperate environments where winters bring cold temperatures and snowfall (e. g. the common pitcher plant – Sarracenia purpurea), others lay their traps along the soil (Genlisea) or thrive in desert-like conditions and on calcium-rich limestone deposits (e. g. the Portuguese dewy pine – (Drosophyllum lusitanicum) and butterwort – (Pinguicula valisneriifolia), respectively, while some tropical pitcher plants belonging to the Nepenthes genus grow vines up to hundreds of feet long with traps that can capture “creatures as large as frogs [and even] some birds and rodents. ”[3]

Traps:

Carnivorous plants can be divided into two major groups based on the type of trap they use – passive or active.

 Passive Traps:

There are three types of passive traps – “pitfall, ” “lobster-pot, ” and “flypaper” or “adhesive” – which do not use an active means such as motion or movement to trap prey. Instead they generally rely on “foraging” insects (e. g. ants, beetles, butterflies, flies, moths, and wasps) to enter and become ensnared. Carnivorous plants utilizing passive traps include the cobra lily (Darlingonia), pitcher (Sarracenia), sun pitcher (Heliamphora), and tropical pitcher (Nepenthes) plants, as well as the Portuguese dewy pine (Drosophyllum) and Australian rainbow plant (Byblis).

§ Pitfall Traps:

The first type of passive trap is the “pitfall” trap, the classic representation of the group. These traps generally utilize “elongated tendrils bearing ‘pitcher’ traps at their tips, ” in which each “‘pitcher’ or “rolled leaf” [consists of] a thickened rim and a lid at the apex. ”[4] When prey enters, it is ensnared by “downward-pointing hairs” and slippery walls that push it into a pool of digestive enzymes and/or bacteria”[5] that expedite decomposition and amino acid absorption.

The sun pitcher (Heliamphora) has the simplest “pitfall” trap, which merely consists of a rolled leaf with sealed margins and a tiny operculum (flared leaflet that covers the trap’s opening) and gap (which allows for water overflow) because of the high rainfall in its natural habitat. Because of its simplicity, the sun pitcher (heliamphora) relies solely on symbiotic bacteria to digest its prey and provide nutrients.

The cobra lily (Darlingonia), pitcher (Sarracenia), and epiphytic (orchid-like plants that grow on other plants solely for mechanical support) tropical pitcher (Nepenthes) plants utilize more complex “pitfall” traps to capture and kill prey.

Pitcher plants (Sarracenia) utilize traps resembling “open funnels” consisting of “colorful areas around the opening [that] are patterned like flowers and heavily smeared with rich nectar to entice… bees, wasps, beetles, ants, and moths” to enter. Inward pointing hairs then direct prey deeper into their tube until they encounter “a waxy smooth surface” sliding into a pit consisting of water and enzymes where they drown and are digested. [6]

Two Sarracenia species, (flava and burgundy flava, the latter which gets its name from the presence of anthocyanins, a pigment giving its pitchers a reddish color) also utilize coniine, a toxic alkaloid found in the hemlock, to enhance the effectiveness of their traps by poisoning their prey.

While the common pitcher plant (Sarracenia purpurea), a low-growing carnivous specimen (6 to 12 inches at most) relies on open-funnel pitchers to “catch rainwater to drown its victims”[7] higher growing pitcher plants such as the yellow pitcher (Sarracenia flava), white trumpet (Sarracenia leucophylla), hooded pitcher (Sarracenia minor), and sweet pitcher (Sarracenia rubra), which can grow anywhere from 8 to 48 inches in height depend on “rain hoods” or opercula (flared leaflet coverings) to protect their traps from overfilling with water and toppling over.

The cobra lily (Darlingonia) uses a “balloon-like” chamber pitted with areolae (small colorless “chlorophyll-free [spaces] through which light can penetrate”) to confuse prey attempting to escape. Insects enticed by “fish-tail like” operculum outgrowths enter a chamber via an opening underneath the balloon. Once inside, they tire themselves trying to escape from the false exits (areolae), until they eventually fall into the tube”[8] at the bottom of the pitcher, where they are digested.

Finally since the last type of pitcher plant – Nepenthes uses their leaf-stems rather than their leaves (which have a significantly smaller concentration of chloroplasts) for photosynthesis, elevating the importance of captured prey, they use “pitchers” ranging in “size from egg cup to beer glass” to store water and trap insects (mainly ants, beetles, and centipedes), spiders, small animal life (e. g. frogs and other small amphibians) and even occasionally small stricken birds or rats “that easily lose their footing on the smooth surface of the pitcher’s lip, slipping and drowning in the [digestive enzymes] inside the flower”[9] to obtain “nutrients that are rare in the rainforest. ”[10]

Interestingly, though, when it comes to Nepenthes, not all insects that fall into their pitchers drown or serve as food. Some insect species and their larvae “have developed a resistance to the [Nepenthes’] digestive enzymes and even choose to live there, competing with the host plant for food… eating drowning victims. ”[11]

One Nepenthes species, the “fanged pitcher plant” (Nepenthes bicalcarta) not only permits ants to enter and leave to harvest dead prey to prevent an overbuildup of organic matter that could lead to pitcher rot, but also deploys “two sharp spines [nectar glands] on the underside of the [pitcher] lid”[12] to inhibit prey from escaping.

Another species that uses a “pitfall” trap is the bromeliad (Brocchinia reducta), a relative of the pineapple. It uses an urn “formed from tightly-packed, waxy leaf bases of the strap-like leaves”[13] to collect water and capture and kill insects, which are then broken down by nitrifying symbiotic bacteria, in which both organisms benefit from the prey’s nutrients.

§ Lobster-Pot Traps:

The second type of passive trap is the “lobster-pot” trap, which utilizes “a ‘Y-shaped’ modified leaf” that permits easy entrance and no escape. Once prey enters, inward pointing hairs and an internal water flow created by a vacuum similar to that in bladderworts (Utrichularae) force it into “twisted tubular channels” that are coiled “around the upper two arms of the ‘Y’ until it proceeds towards the ‘stomach’ and digestive glands at the “lower arm of the ‘Y’” where it is digested. [14]

Lobster-pot traps are found in corkscrew (Genlisea) and parrot pitcher plants (Sarracenia psittacina), both of which specialize in the capture and digestion of aquatic protozoa. In the case of the corkscrew (Genlisea), protozoa are attracted by the plant’s secreted chemicals and yellow or violet flowers. Upon swimming into a “trapping leaf” that hangs downward in wet soil and/or water through narrow slits, escape is blocked by inward pointing hairs. Afterwards glands lying between these hairs secrete enzymes to digest the prey.

§ Flypaper or Adhesive Traps:

While the final type of passive trap is the “flypaper” or “adhesive” trap in which plant leaves are covered with “sticky, gland-tipped hairs (which can simultaneously trap, digest, and absorb multiple amounts of small flies) or a sticky viscid (fluid-like) glue-like layer of mucilage” (adhesive gelatinous plant substance) which hopelessly ensnare struggling victims” it must be noted that some “flypaper” or “adhesive” traps are “active. ”

Both the Portuguese dewy pine (Drosophyllum) and the Australian rainbow plant (Byblis) use passive “flypaper” or “adhesive” traps. Consisting of leaves that are “incapable of rapid movement and growth” they solely rely on sticky gland-tipped hairs and adhesive viscid mucilage, respectively to capture and digest prey.

 Active Traps:

There are three types of active traps – “snap, ” “trapdoor” or “bladder/suction, ” and “flypaper” or “adhesive” – all of which require movement or motion to capture prey. Carnivorous plants utilizing active traps are the venus fly trap (Dionaea muscipula), waterwheel (Aldrovanda vesiculosa), bladderwort (Utricularia), sundew (Drosera), and butterwort (Pinguicula).

§ Snap Traps:

The first type of active trap is the “snap” trap, the classic representation of the group. The venus fly trap (Dionaea muscipula) and aquatic waterwheel (Aldrovanda vesiculosa) are the classic plants of this group. They utilize “hinged leaves” consisting of two mid-lobes, which fold closed along their midrib when prey triggers “bristle-like [stiff] hairs near the middle of [their] upper side due to a rapid loss of turgor (pressure) within the epidermal leaf cells on the upper side of the leaf [due to the rapid pumping of ions]… (as long as an adequate supply of ATP (adenosine triphosphate) is present. ” Once closed, the “fringe of stiff hairs around the edge of the leaf blade become interlocked… trapping the prey. Then as it struggles, the lobes grow tighter until hermetically sealed to form a stomach where digestive enzymes from secretion glands… break down its proteins. ” This is especially important for the venus fly trap (Dionaea muscipula) since the soil where it grows is too acidic for “nitrifying bacteria” and thus nitrogen (N). [15]

§ Trapdoor or Bladder/Suction Traps:

The next type of active trap is the “trapdoor” or “bladder/suction” trap utilized by the bladderwort (Utrichularia), a submerged aquatic plant. It is “one of nature’s most precise and delicate traps, and certainly the most rapid, ” snapping shut in only 1/60th of a second. Consisting of hundreds of tiny “pear-shaped” bladders (ranging in size from 2 to 4 millimeters) attached to “feathery submersed branchlets (modified leaves) by tiny stalks, the bladderwort (Utrichularia) along with Aldrovanda, another aquatic carnivorous plant, trap rotifers (tiny aquatic organisms – Rotifers), daphnia (water fleas), and mosquito larvae that unsuspectingly swim through an open entrance. [16]

Each tiny bladder/suction trap, consists of an “inward opening door” that hangs from the top of its opening. “Support tissue and a mucilage (adhesive gelatinous plant substance) coating around the door frame helps to seal the door [when snapped shut] and prevent water entry. The door opening is surrounded by several bristly hairs [while] numerous, tiny glands inside the bladder absorb most of the internal water and expel it on the outside” creating a “partial vacuum” within the bladder. At the same time, “the airtight door is hinged to allow easy entry… Special trigger hairs near the lower free edge of the door cause it to open. When a tiny aquatic organism touches or hits one of these extremely sensitive hairs, the hair acts as a lever, multiplying the force of impact and bending or distorting the very pliable door. This breaks the watertight seal…” which then aided by the presence of a “partial vacuum, ” sucks the unsuspecting prey into the trap. Afterwards the prey cannot force the “trapdoor” open to escape. [17]

§ Flypaper or Adhesive Traps:

The final type of active trap is the “flypaper” or “adhesive” trap, which is passive in some species. When an insect lands on the shiny surface of the mucilage glands of a sundew (Drosera), it rapidly responds with thigmotropic (a bending or turning) action that causes the leaf blade to form a “shallow digestive pit. ”[18]

A second plant utilizing an active “flypaper” or “adhesive” trap is the butterwort (Pinguicula), which relies on sticky viscid layers of mucilage to capture moths, flies, fungus gnats, and other small flying insects that are ultimately digested by “short and nondescript”[19] secreting glands.

Hermaphrotropism:

Carnivorous plants are generally “hermaphrotrophic” since they share autotrophic (they engage in photosynthesis converting water, sunlight, carbon dioxide (CO2) and simple minerals into energy and starch) and heterotrophic (parasitic – harvesting a living host for nutrients while offering no benefit in return or saprophytic – “deriving nourishment from dead or decaying organic matter, ”[20] thus utilizing “organic molecules” that have been “reprocessed by other organisms”[21]) characteristics.

While carnivorous activities are not vital for the vast majority of these plants, which can survive on photosynthesis alone, heterotrophic activities are beneficial since they provide added nutrients to account for their higher rate of respiration (expending of energy on “non-photosynthetic structures [such as] glands, hairs, glue and digestive enzymes”[22]). Based on lab studies, carnivorous plants that had been grown without “insect” food were found to exist just fine. However when insects (sources of nitrogen (N) phosphorous (P), and sometimes Potassium (K)) were added to their diet, they exhibited faster growth and produced larger quantities of seeds.

The pygmy sundew (Drosera burmannii) and Genlisea species of the bladderwort family are exceptions. The former cannot obtain nitrates from soil due to the absence of nitrate reductase and other essential enzymes for absorbing them) while the latter (found in “nutrient-poor white sands and moist rock outcrops in South America and tropical Africa”)[23] is rootless and lacks chlorophyll. Accordingly both obtain nutrients solely from the capture of prey (insects in the case of the pygmy sundew (Drosera burmannii)) and protozoa (in the case of the Genlisea bladderwort species).

Basically when it comes to carnivorous plants and fungi, the lower the quantity of soil nutrients and the higher the quotient of sunlight and rainfall, the greater their reliance on carnivory. Accordingly most carnivorous plants grow where sunlight and water are plentiful and nutrients such as nitrates and phosphates are low.

Some carnivorous plants, most notably members of the Sarracenia species, tuberous sundews, bladderworts, and butterworts even temporarily give up carnivory when conditions are not optimal. When soil nutrient levels rise and sunlight levels diminish, many Sarracenia and butterwort species grow “flat, non-carnivorous leaves (phyllodes), ” which are more efficient with photosyntheis, while tuberous sundews revert to tubers (localized rounded knobs) during times of drought, and bladderworts into turions (fleshy shoots) during winter rather than expending energy to produce “inefficient, damaged traps. ”[24]

Carnivorous Fungi:

In addition to carnivorous plants, carnivorous saprophytic fungi that trap and kill prey also exist. Currently there are over 200 known species of carnivorous fungi – zygomycetes, basidiomycetes, and hyphomycetes. Carnivorous fungi use two types of traps – “active” consisting of constricting rings (filamentous loops) and “passive” comprised of adhesive, sticky pads.

Fungi belonging to the Zygomycota phylum (zygomycetes) consist of “a mass of intricately branched filaments (mycelium)” that attack dead flies and tiny living organisms. Examples are the Dactylaria species, which capture and kill tiny nematodes (eelworms) and Dactylella tylopaga that feast on “microscopic amoebas in the soil. ”[25]

While some of these fungi passively captures prey through the use of hundreds of “adhesive” sticky pads, the Dactylaria species uses an active method. When a tiny nematode (eelworm) slithers into a filamentous loop and attempts to nibble on the fungus for food, the loop, triggered by a sudden chemical reaction tightens like a lasso, trapping it. Afterwards, when the struggling nematode (eelworm) dies, the fungus penetrates its body, digesting and absorbing it.

Movement Mechanisms in Carnivorous Plants and Fungi:

Carnivorous plants with active traps generally use one of three types of movement mechanisms: Change in cell size initiated by “acid growth” (e. g. venus fly traps (Dionaea muscipulae), in which the repeated touching of one or more hairs unleashes an “acidic” reaction “causing the outside surface of the trap to [become] larger than the inside wall” leading to its “snapping shut (corroborated by experiments showing that repeated stimulation causes “trap fatigue” or a slowed closing)), cell growth motion (e. g. sundews (Drosera), in which tentacles “bend towards prey because the cells on one side [of the tentacle]… outgrow the cells on the other”), and chemical reactions (e. g. Dactylaria, in which chemical reactions trigger filamentous loops to snare their prey). [26]

Digestion:

Most carnivorous plants and fungi manufacture their own enzymes to dissolve proteins found within their prey. Commonly produced enzymes are acid phosphatase, amylase, esterase, and protease.

However some such as the common pitcher plant (Sarracenia purpurea) and the fanged pitcher plant (Nepenthes bicalcarta), to name two, rely on a symbiotic (both organisms benefit versus parasitism in which the one organism benefits at the expense of a host) relationship with bacteria that digests dead, rotting prey, providing “decomposed molecules” for nutrition. At the same time, sundews (Drosera) rely on a symbiotic relationship with arthropods (most notably assassin bugs) that ingest dead prey to produce nutrient-rich excrement.

Conclusion:

Carnivorous plants and fungi are “fascinating [and] intriguing” because of their unique nature that involves matching wits with living organisms belonging to the animal and protozoa kingdoms. Though first studied in depth by Charles Darwin in 1875 and despite the lack of fossil evidence, it is known that carnivorous plants and fungi “evolved independently of many plant [or fungal] lineages” in their own separate way: “Pitfall traps evolved independently (convergent evolution) in four plant groups (the eudicot orders Caryophyllales, Oxalidales, Ericales, and the monocot family Bromeliaceae)… and sticky traps in at least three [plant groups] (the Caryophyllales, Ericales, and Lamiales). [At the same time snap traps and lobster-pot traps] evolved only once among carnivorous plants. ” Many, though still remain poorly studied (e. g. Ibicella lutea have not been studied since 1916 leaving it open whether they are truly carnivorous) with more research needed.

Last, these plants and fungi are not immune to destruction. They face threats from parasites (e. g. aphids and mealybugs), infections from grey mold (Botrytis cinerea), and “habitat destruction and over collection. ”[27] Unless conservation methods are enacted, which include rainforest preservation, some carnivorous species are tragically likely to become extinct, depriving the world of marvels and intrigue.

_

[1] Barry Rice. The Carnivorous Plant FAQ. April 2002. 21 June 2006. http://www.sarracenia.com/faq/faq1040.html

[2] Carnivorous Plant. Wikipedia.com and Carnivorous Plants/Insectivorous Plants. Botanical Society of America

[3] Barry Rice. The Carnivorous Plant FAQ. April 2002. 21 June 2006. http://www.sarracenia.com/faq/faq1160.html

[4] W. P. Armstrong. Carnivorous Plants.

[5] Carnivorous Plant. Wikipedia.com.

[6] William Cullina. Wildflowers: A Guide to Growing and Propagating Native Flowers of North America. (Houghton Mifflin Company, Boston, 2000) 182.

[7] William Cullina. Wildflowers: A Guide to Growing and Propagating Native Flowers of North America. (Houghton Mifflin Company, Boston, 2000) 182.

[8] Carnivorous Plant. Wikipedia.com.

[9] Edward G. Atkins, Ph. D. The Plight of the Tropical Rainforest: Vanishing Eden. Barron's. October 1991. 171.

[10] Edward G. Atkins, Ph. D. The Plight of the Tropical Rainforest: Vanishing Eden. Barron's. October 1991. 171.

[11] Edward G. Atkins, Ph. D. The Plight of the Tropical Rainforest: Vanishing Eden. Barron's. October 1991. 171.

[12] Nepenthes bicalcarata. Wikipedia.com

[13] Carnivorous Plant. Wikipedia.com.

[14] Carnivorous Plants/Insectivorous Plants. Botanical Society of America.

[15] W. P. Armstrong. Carnivorous Plants.

[16] W. P. Armstrong. Carnivorous Plants.

[17] W. P. Armstrong. Carnivorous Plants.

[18] Carnivorous Plant. Wikipedia.com.

[19] Carnivorous Plant. Wikipedia.com.

[20] saprophyte. Dictonary.com.

[21] Barry Rice. The Carnivorous Plant FAQ. April 2002. 21 June 2006. http://www.sarracenia.com/faq/faq1100.html

[22] Carnivorous Plant. Wikipedia.com.

[23] W. P. Armstrong. Carnivorous Plants.

[24] Carnivorous Plant. Wikipedia.com.

[25] W. P. Armstrong. Carnivorous Plants.

[26] Barry Rice. The Carnivorous Plant FAQ. April 2002. 21 June 2006. http://www.sarracenia.com/faq/faq1320.html

[27] Carnivorous Plants/Insectivorous Plants. Botanical Society of America.

Sources:

Barry Rice. The Carnivorous Plant FAQ. April 2002. 21 June 2006. http://www.sarracenia.com/faq.html

Carnivorous Plant. Wikipedia.com. 2006. 21 June 2006. http://en. wikipedia.org/wiki/Carnivorous_plant

Carnivorous Plants/Insectivorous Plants. Botanical Society of America. 21 June 2006. http://www.botany.org/carnivorous_plants

Edward G. Atkins, Ph. D. The Plight of the Tropical Rainforest: Vanishing Eden. Barron's. October 1991

Nepenthes bicalcarata. Wikipedia.com. 2006. 21 June 2006. http://en. wikipedia.org/wiki/Nepenthes_bicalcarata

saprophyte. Dictionary.com. Lexico Publishing Group, LLC. 2006. 21 June 2006. http://dictionary. reference.com/search?q=saprophytic

W. P. Armstrong. Carnivorous Plants. 21 June 2006. http://waynesworld. palomar. edu/carnivor.htm

William Cullina. Wildflowers: A Guide to Growing and Propagating Native Flowers of North America. (Houghton Mifflin Company, Boston, 2000).

William Sutherland is a published poet and writer. He is the author of three books, “Poetry, Prayers and Haiku" (1999), “Russian Spring" (2003) and “Aaliyah Remembered: Her Life & The Person behind the Mystique" (2005) and has been published in poetry anthologies around the world. He has been featured in “Who's Who in New Poets" (1996), “The International Who's Who in Poetry" (2004), and is a member of the “International Poetry Hall of Fame. " He is also a contributor to Wikipedia, the number one online encyclopedia.

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