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This Issue Of Wayne's Word Is |
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Metallic Blue-Green Blowflies To Their Showy Petals. |
| DISCLAIMER: The staff at WAYNE'S WORD assumes no responsibility for using any of the following flowers in a bouquet, corsage or floral arrangement. The size and weight of some of these blossoms could cause serious back injury if they are pinned to your lapel. In addition, they could negatively affect a loving relationship with a friend or spouse, especially when their floral stench attracts carrion insects and maggots. [W.P. Armstrong, 1 June 1996] |
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A typical flower may be stereotyped as a colorful, sweet-smelling structure that attracts insects. A variety of insects find the showy
petals and fragrance irresistible, and the reward for their pollination
service is a carbohydrate-rich, sugary nectar secretion from the flower.
While the above scenario fits the majority of flowering plants, there are
many notable exceptions. Some plants rely on wind or water for
pollination, and produce inconspicuous flowers with copious airborne or
water-dispersed pollen. But of all the exceptions to the typical flower
stereotype, some of the most remarkable are known as "carrion flowers,"
showy blossoms with the stench of rotting flesh.
1. What Is A Carrion Flower?Unlike the fragrant blossoms that attract bees, butterflies and moths, carrion flowers simulate the odor of a rotting carcass and attract carrion beetles and a variety of flies including blowflies, flesh flies and midges. Not only do these flowers smell like a dead animal, but their petals are typically flesh-colored, often with a dense covering of hair. The orchids Bulbophyllum and Pterostylis contain spot patterns or "warts" that imitate clusters of flies already enjoying a meal, and movable parts in the flower that catapult or maneuver the fly into a position of contact with the pollen masses (pollinia) or receptive stigma. Although not true carrion flowers, there are many other species with slightly malodorous flowers that attract flies, including a number of orchids and the male flowers of carob trees (Ceratonia siliqua).
2. Why Do Some Carrion Flowers Smell Like Flatulence?Carrion insects feed on feces, rotting flesh and other decaying organic matter, and they also lay their eggs in these damp, putrid-smelling places. Carrion flowers are masters in the art of deception because they lure these insects into their blossoms. The flowers get pollinated but the fate of the insects is much more dismal--maggots hatching from eggs laid by them will perish from lack of any suitable food. Unlike typical insect-pollinated flowers, most carrion flowers do not waste precious energy on rewarding its pollinators with copious nectar. Blossoms of certain members of the arum family (Araceae) release volatile dimethyl oligosulphides to attract blowflies. The overpowering stench of some carrion flowers may be caused (in part) by putrescine (1,4-butanediamine) and cadaverine (1,5-pentanediamine), relatively simple amine compounds derived from the amino acids ornithine and lysine. These potent, foul-smelling amines are also produced during the decomposition of rotting proteins. One of the warning tests for deadly botulism poisoning in spoiled food is the presence of rotten-smelling amines produced by proteolytic strains of the anaerobic bacterium Clostridium botulinum. Amines are also produced by the action of intestinal bacteria and are often released in a flammable mixture of volatile gases (including carbon dioxide, hydrogen, hydrogen sulfide and methane) during the phenomenon known as flatulence. In fact, some of these noxious gasses and incompletely oxidized hydrocarbons do not meet the emission control standards established by the Environmental Protection Agency (EPA). It has been suggested that serious flatulence offenders should be required to pass stringent biennial smog control sniffer tests, just like internal combustion air pollution devices.
3. The Perception Of Odors By Different AnimalsIt is interesting to speculate about how different species of animals perceive odors, and why certain putrid odors are repugnant to us but are irresistible to carrion insects. Whether a particular odor is perceived as "bad" or "good" is in the nose of the beholder. In the case of humans, there is certainly an innate or learned adaptive advantage in associating foul-smelling food with illness and disease-causing microbes; however, blowflies perceive these same odors as a potential meal for themselves and their ravenous maggot offspring. The actual triggering mechanism that excites female flesh flies and blowflies (families Sarcophagidae and Calliphoridae) to lay their eggs in damp, putrid places, such as fresh feces and carrion, is probably a lot more complicated. During warm weather, egg-laying blowflies can locate a dead carcass or stinking flower within hours. They can smell the odor of a fresh, rotting carcass up to a mile away. Generally, blowflies are not as strongly attracted to a carcass that has mummified due to prolonged desiccation in dry weather. Even with external mummification, the carcass may be attractive to blowflies if the abdominal cavity is torn open by carnivores or scavengers. The stages (larval instars) of maggot development can be used to approximate the age of a rotting animal carcass. Each larval instar has a time window before it molts (sheds its chitinous exoskeleton) and develops into a second (larger) stage. In typical blowflies there are three distinctive larval instars before the maggot stops feeding and undergoes metamorphosis into a pupa within a protective chitinous skin (puparium). During pupation, the pupa transforms into an adult male or female blowfly which exits the puparium and flies away to mate. Depending on the precise stages of blowflies that are found on a carcass or during an autopsy, the forensic entomologist can simply count back to determine the approximate date when the deceased body was available to egg-laying flies. This evidence was crucial testimony for the defense in the San Diego trial of David Westerfield; however, after hundreds of hours of testimony, the jury found Westerfield guilty.
4. Why Do Some Carrion Flowers Incarcerate Insects?In some carrion flowers the insects are lured into dark openings leading to the putrefying interior where they become trapped among the floral organs. This strategy insures cross pollination, especially when the male anthers release pollen several days after the female stigma is no longer receptive. When the imprisoned insects are allowed to leave they are given a thorough dusting of fresh pollen to be taken to a different plant. One of the classic insect-trapping carrion flowers is the European Dutchman's pipe (Aristolochia clematitis), a member of the Birthwort Family (Aristolochiaceae). The unusual common names are derived from the curious blossoms with a shape reminiscent of Sherlock Holmes' pipe, and an old herbal remedy. Some species in this family have aromatic roots that were reputedly used as a purgative to induce labor, a questionable practice that is not recommended. The curious blossoms of some species superficially resemble a human fetus in the womb, and the plants were once thought to facilitate child birth. During medieval times, various ailments were treated with plants that resembled certain afflicted parts of the body. This practice was called the "Doctrine of Signatures," and became the basis of medical treatment for centuries to come. The striking, tubular flower of Dutchman's pipe is held upright as it emits a foul, pungent odor. Small gnats land on the vertical upper calyx surface but slip down through the floral tube and into the inflated "pipe chamber" due to slippery wax granules on the inner surface. Dense, downward-pointing hairs in the floral tube prevent the gnats from climbing out. During their incarceration the gnats receive rations of nectar. Several days later, when the anthers release pollen, the jail hairs wilt and the flower tilts horizontally, allowing the pollen-laden gnats to walk out of their prison, and into another receptive floral trap on a different plant.
There are approximately 350 species of Aristolochia, mostly from tropical regions of the world. Many species have ingenious insect traps and malodorous, often nauseating stenches when the blossoms first open. One of the largest and most bizarre flowers on earth is the Brazilian Dutchman's pipe (A. gigantea). The showy maroon calyx-like corolla is the size of a large dinner plate (30 centimeters) across), with an "inviting" orifice leading into an inflated, bladder-like trap. Another unusual Dutchman's pipe native to northern California (A. californica) has much smaller blossoms that are pollinated by fungus gnats.
5. The Foul-Smelling Starfish Flowers Of AfricaSome of the most notorious carrion flowers belong to the Milkweed Family (Asclepiadaceae), a very diverse plant family characterized by milky-white sap. Several South African succulent genera, including Stapelia, Caralluma and Huernia, resemble spineless, sprawling cacti with strange starfish-shaped flowers. The flesh-colored, hairy blossom of S. gigantea may be 8 to 10 inches across (20-25 cm), with a nauseating stench. Fringes of soft white hairs on the reddish-brown petals superficially resemble a layer of mold growing on rotting matter (at least through the compound eyes of carrion insects). Occasionally grown in southern California, the curious flowers attract flies and maggots when they are in full bloom. Another South African species, S. flavirostris, has strange blossoms that look and smell more like a furry, dead animal than a flower. The striped "zebra flowers" Huernia zebrina also produce an intensely fetid odor as they lie on the desert sands of South Africa. Another genus of climbing milkweeds (Ceropegia) produces striking, malodorous blossoms shaped like a wine glass, often with glistening cilia to attract flies. Like Aristolochia, they detain their visiting flies until the male flowers are mature.
A Fungus That Also Attracts Green Bottle Flies
6. The Rank And Remarkable ArumsThe Arum Family (Araceae) is a large tropical family containing many popular cultivated genera, including Anthurium, Caladium, Philodendron, and Dieffenbachia. It also contains some of the most fascinating and bizarre carrion flowers on earth. Like the common garden calla, Zantedeschia aethiopica, the small unisexual flowers are packed along the base of an erect, phallus-like central spadix, typically with male flowers above the female. The spadix emerges from a vase-shaped or funnel-like modified leaf or spathe which is often brightly colored. Probably the best-known North American species is the skunk cabbage (Symplocarpus foetidus) of the eastern United States. A showy western skunk cabbage (Lysichiton americanum), with a bright yellow spathe, has a somewhat skunky odor, but not really the offensive stench of its eastern counterpart. The "skunk cabbage meadows" depicted on trail guides to the southern California mountains actually refers to corn lilies (Veratrum californicum), a member of the Lily Family (Liliaceae). The European relatives "lords-and-ladies" (Arum maculatum) and "dragon arum" (Dracunculus vulgaris) emit rather unpleasant odors resembling carrion or fresh feces. They are definitely not recommended in a bouquet or floral arrangement--unless you are trying to convey a message from a jilted lover. Although these plants are inconspicuous most of the year, their showy spathes and stench are unmistakable during late spring and summer.
7. The Amazing Flynapping Arum Of Sardinia
Another remarkable arum called "dead-horse arum" (Helicodiceros muscivorus) with an ingenious fly trap is native to the rocky Mediterranean islands of Sardinia and Corsica. With a stench reportedly as strong as a sheep carcass, blowflies are lured into the fetid aperture at the base of the funnel-like spathe. Behaving as they would in a real carcass, the flies force their way into the neck past the spadix and down into the pitch-dark chamber itself. Carrying pollen from another plant, they inadvertently pollinate the
receptive female flowers at the base of the chamber. Unable to escape from
the chamber due to a dense rosette of stiff hairs, the flies remain
prisoners until the male flowers above the stiff hairs start to release
pollen. Then the barricade of hairs wilts and the flies are able to
escape, getting dusted with pollen as they leave the damp and putrid-smelling chamber.
A brief article about olfactory mimicry in Helicodiceros muscivorus appeared in Nature 420: 625 (12 December 2002) by M.C. Stensmyr, I. Urru, I. Collu, M. Celander, B.S. Hansson and A-M. Angioy of the Swedish University of Agricultural Sciences. The authors determined the precise odor that attracted blowflies of the family Calliphoridae to the inflorecence of this species. Blowfly antennae were stimulated by three similar oligosulphides: dimethyl monosulfide (DMMS), dimethyl disulfide (DMDS) and dimethyl trisulfide (DMTS). All three volatile compounds were identified using gas chromatography (GC) with simultaneous flame ionization detection (FID). These oligosulphides are also produced by decaying meat during protein decomposition. The identical antennal responses to arum and carcass odors indicate that a carrion fly cannot rely on odors alone to separate the model (decaying meat) from the olfactory mimic (arum inflorecence). This is yet another example of sexual deception where the plant exploits insects for pollination purposes. It is interesting to note that DMMS is a primary irritant in humans. DMDS and DMTS are volatile compounds found in onions and garlic. In small concentrations, they are also important flavor components of grain spirits such as whiskey.
8. The World's Largest And Stinkiest Arum
Although the blossom of this arum may tower over an adult human, it is not the world's largest flower. It is technically an inflorescence composed of numerous small, unisexual male and female flowers clustered around the base of the spadix, within the showy, funnel-shaped spathe. Female flowers consist essentially of ovule-bearing pistils deep within the spathe. Staminate (male) flowers (consisting essentially of stamens) are packed around the spadix, just above the female flowers. The conspicuous upper part of the spadix is sterile (flowerless) and emits the stench. Since the male and female flowers reach maturity at different times, cross pollination between different plants is the normal mechanism for sexual reproduction and seed production. Female flowers are typically receptive before the anthers release pollen, a cross pollination incentive known as protogyny. After pollination, the minute female flowers give rise to several hundred seeds. Although truly magnificent, this inflorescence is rather small compared with the Bolivian bromeliad Puya raimondii, with a flower stalk 35 feet (11 m) tall bearing over 8,000 white blossoms. In case you are wondering about the generic name Amorphophallus, it is derived from the Greek words "amorphos" (shapeless) and "phallos" (penis). Actually, the 8 foot phallus-like spadix of A. titanum rivals the size of a blue whale penis. This remarkable arum flowered in spring of 1996 at the University of Bonn Botanical Garden in Bonn, Germany.
On August 2, 1999 an Amorphophallus titanum achieved full bloom at the Huntington Botanic Garden in San Marino, California. This was only the 11th recorded bloom in the United States and the first ever in California. Equally astonishing was the number of people who came to visit this magnificent plant on the peak day of its blooming period, over 10,000 admirers. They waited patiently in a long line in 80-90 degree heat, a line that at one time extended the length of two football fields (or about 200 meters). Some people wore protective nose masks, and one boy even wore a gas mask. Actually, no one was overcome by the stench (the plant was roped off to prevent people from getting their faces too close to the funnel-shaped spathe).
On the 14th of June 2000, another remarkable Amorphophallus titanum was in full bloom at the Fullerton Arboretum on the campus of California State University at Fullerton (CSUF) in Orange County, California. Known affectionately as "Tiffy Titan," the plant came from one of two tubers donated to the CSUF Department of Biological Science in October 1994. [Incidentally, Tiffy's name is derived from Titan, the mascot for CSUF.] Both tubers came from seeds that were planted the previous year. The typical life cycle of A. titanum starts with a seed that develops into a dormant tuber, followed by leaf production, larger dormant tuber, flowering and seed production. At CSUF, the complete life cycle has taken seven years. Pollen from another A. titanum that bloomed the previous summer (1999) at Huntington Botanic Garden was applied to all of the female flowers of "Tiffy Titan" at the peak day of flowering (14 June 2000).
On July 16, 2002 another spectacular Amorphophallus titanum came into full bloom at Quail Botanical Gardens in Encinitas, California. The blossom (inflorescence) developed from a huge, tire-sized tuber in a large flower pot. As the spathe opened into a reddish-purple funnel surrounding the yellow spadix, the blossom emitted a powerful carrion stench that filled the air of this serene botanical garden.
One of the original two tubers of Amorphophallus titanum donated to CSUF was still in its leaf stage on June 14, 2000 when "Tiffy Titan" was in full bloom. The single, enormous compound leaf was approximately eight feet tall (2.4 m) with a spread of at least 8 feet (2.4 m). It was already brown and withered, and was near the end of its leaf stage. Following the leaf stage, the enlarged tuber of this second A. titanum (with sufficient carbohydrate reserve) will hopefully produce another striking, stinking blossom.
9. A Stinking Root Parasite From AfricaAnother interesting carrion flower Hydnora africana, a root parasite on shrubby species of Euphorbia in arid deserts of South Africa, attracts herds of carrion beetles. The salmon-red, flesh-colored flowers emerge from the sand and become literally crammed with black beetles. This curious flower belongs to the Hydnoraceae, a small family of unusual root parasites, some of which look more like the fruiting bodies of soil fungi than flowering plants. Another species (H. abyssinica) commonly parasitizes the roots of Acacia.
10. The Stinking Corpse Lily: World's Largest FlowerA related family of parasitic flowering plants (the Rafflesiaceae) contains the "stinking corpse lily" (Rafflesia arnoldii), the world's largest individual flower and truly a wonder of the plant kingdom. It has been called the "giant panda of the plant world" because this rare and endangered species only occurs in the rain forests of Sumatra and Borneo in the Malay Archipelago. Unlike most flowering plants, it has no leaves or stems and grows endoparasitically within the woody stems of its host vine Tetrastigma, a relative of the grape. Unless you saw evidence of an old blossom, you could walk right past a Tetrastigma vine without ever knowing that a complete Rafflesia plant lives inside its stem. Occasionally a large flower bud resembling a pale orange cabbage breaks through the bark of the host vine and expands into an enormous blossom up to 3 feet (0.9 m) in diameter and weighing up to 25 pounds (11 kg). The gigantic unisexual flower has five fleshy red lobes (sepals) spattered with raised white spots. With an odor reminiscent of a stinking corpse, the blossom attracts carrion beetles and flies which shuttle the pollen from male to female flowers. A single female flower may produce up to four million seeds which are dispersed by a variety of animals, from ants, tree shrews and squirrels, to the feet of wild pigs and Asian elephants. If a seed becomes lodged in a moist crevice on its host vine, it germinates and penetrates the host tissue where it proliferates into a network of microscopic filaments of cells. These fungus-like networks of vascular tissue eventually give rise to a mammoth blossom that pushes out through the host stem, making Rafflesia one of the most intriguing and unusual plants on earth. The chances of a seed finding a host vine are slim, and massive deforestation has further decreased the odds of this remarkable event. Recently the governments of Indonesia and Malaysia have begun to recognize the marketable curiosity value of this plant and ecological preserves are being established.
11. Pilostyles: California Relative Of Largest FlowerIronically, a seldom-seen relative of Rafflesia grows in the Anza-Borrego Desert region of southern California. It is called Pilostyles thurberi, and like its Malaysian counterpart it grows completely within its host's stem. Only in the case of Pilostyles the host is a small, leguminous shrub called dyeweed (Psorothamnus emoryi). Like Rafflesia, male and female flowers appear from buds that break through the host stem, but quite unlike its gargantuan cousin, the fleshy red flowers are only about 3 to 5 millimeters in diameter. When they appear on the host stem, the buds of Pilostyles resemble small reddish pimples, but unlike a case of severe acne, the "pimples" open into minute blossoms.
12. Putrid Flowers Of The Indian AlmondStinking flowers are by no means limited to herbaceous perennials. In fact, a large rain forest tree of the Old World tropics called Indian almond (Sterculia foetida) produces masses of small, reddish-orange flowers with a disagreeable putrid stench. It belongs to the chocolate family (Sterculiaceae) and produces edible seeds inside large, woody pods called follicles. The oily seeds are eaten raw, roasted or fried; however, if consumed in excessive quantities the seeds may have a purgative effect. The smelly blossoms leave a long-lasting, putrid scent in your carrying case or pack. A Costa Rican tree in the custard-apple family (Annonaceae) called "palanco" (Sapranthus palanga) bears cauliflorous blossoms on the main trunk. The flowers are purplish-black when mature and have a strong musky odor resembling a rotting carcass. They are presumedly pollinated by flies or beetles which are attracted to the scent. 
 Flower "scent mimics" that lure carrion insects into their putrid blossoms are some of nature's most fascinating (and successful) experiments in evolution. They certainly represent some of the most fantastic examples of floral diversity. Although they include some of the largest and showiest blossoms in the world, they will probably never be used in a floral arrangement on your dining room table.
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