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Sarraceniaceae :: Sarracenia
 

Sarracenia is a genus comprising the eight (or arguably up to thirteen) species of North American pitcher plants. The genus belongs to the family Sarraceniaceae, which also contains the closely allied genera Darlingtonia and Heliamphora.

Sarracenia are carnivorous plants indigenous to the eastern seaboard, Texas, the Great Lakes area and southeastern Canada, with most species occurring only in the south-east United States (only S. purpurea occurs in cold-temperate regions). The plant's leaves form tall lidded pitchers, which have evolved to trap insects, and which produce enzymes to digest their prey. The insects are attracted by a nectar-like secretion on the lip of pitchers, as well as a combination of color and scent. Slippery footing at the pitchers' rim, aided in at least one species by a narcotic drug lacing the nectar, causes insects to fall inside, where they drown and are digested by the plant as a nutrient source.

In common with many carnivorous plants, Sarracenia usually inhabit permanently wet regions with a low pH whose nutrients, particularly nitrates, are continuously leached away by water or made unavailable by the low pH. Sarracenia consequently gain a competitive advantage over other plants from the substances and minerals they extract from their animal prey.

Morphology and carnivorous mechanism

Sarracenia are herbaceous perennial plants that grow from a subterranean rhizome, with many tubular pitcher-shaped leaves radiating out from the growing point, and then turning upwards with their trap openings facing the centre of the crown. The trap is a vertical tube with a 'hood' (the operculum) extending over its entrance; and below it the top of the tube usually has a rolled lip (the peristome) which secretes nectar and scents. The hood itself frequently produces nectar too, but in lesser quantities.

The inside of the pitcher tube, regardless of species, can be divided into three to five distinguishable zones: zone 1 is the operculum (or hood), zone 2 is the peristome and rest of the trap entrance, while zones 3 and 4 (which in some species are combined) and 5 (only present in S. purpurea) are further divisions of the actual tube. Each of these zones has a specific function, with corresponding morphophysiological characteristics.

  • Zone 1: The Operculum. In most species the operculum covers at least part of the pitcher opening, thereby preventing rain from excessively filling the pitcher, which would result in the loss of prey. The operculum also serves to guide prey to the pitcher opening, using a combination of color, scent, and downward-pointing hairs to guide insects toward the trap entrance. Some species, specifically S. minor and S. psittacina, have opercula which hang low over the pitcher entrance. These are also studded with chlorophyll-free patches, translucent "windows" which confuse prey into attempting to fly through the operculum, thereby causing them to cascade down the pitcher tube. (A similar, more well developed mechanism is found in the closely related Darlingtonia californica).

  • Zone 2: Peristome and trap entrance. This zone is composed mainly of the peristome, which produces copious amounts of nectar, luring insect prey to land or crawl onto the perilous footing surrounding the pitcher trap. This zone also includes the waxy upper portion of the pitcher tube. Footing on this zone is especially sketchy, as the waxy deposits on surface of this zone cause unwary insects loose their footing and tumble into the pitcher depths.

  • Zone 3: Located below Zone 2, this zone features a leaf surface with non-existent footing, as well as a coating of ultra-fine, downward pointing hairs. Insects that have made it this far lose any chance of escape. It is also studded with digestive glands, which secrete digestive enzymes into the digestive fluid.

  • Zone 4: This is the final zone in most species. It is filled with digestive fluids, and readily absorbs nutrients released from the insects by the work of the digestive enzymes and bacteria in the pitcher fluid. Along with more digestive glands, this zone features a thick coating of coarse downward pointing hairs, which makes escape from the digestive fluids impossible.

  • Zone 5: This zone, located below Zone 4 and found only in S. purpurea, is smooth, glabrous, lacks glands, and doesn't serve as an absorbtive zone. Its function is unknown.

Carnivorous mechanism

All Sarracenia trap insects and other prey without the use of moving parts. Their traps are static and are based on a combination of lures (including colour, scent, and nectar) and inescapability – typically the entrances to the traps are one-way by virtue of the highly adapted features listed above.

Most species use a combination of scent, drugged nectar, waxy deposits (to clog insect feet) and gravity to topple insect prey into their pitcher; Coniine, an alkaloid drug narcotic to insects, has been discovered in the nectar-like secretions of at least S. flava. Once inside, the insect finds the footing very slippery with fine wax dustings to the walls of the pitcher. Further down the tube, downward-pointing hairs make retreat impossible, and in the lowest region of the tube, a pool of liquid containing digestive enzymes and wetting agents holds quickly drowns the prey and begins digestion. The exoskeletons are usually not digested, and over the coarse of the summer fill up the pitcher tube.

S. psittacina, the Parrot pitcher, uses a lobster-pot style trap that will admit prey (including tadpoles and small fish during floods) but not allow it to find its way out; and sharp inward-pointing hairs force the victim gradually down to the base of the pitcher where it is digested.

The wide-ranging S. purpurea has no digestive enzymes, but instead obtains nutrients from the digestion and mineralization of nutrients by a complex food web living in the rainwater that collects in each pitcher.

Flowers and seeds

Flowers are produced early in spring, with or slightly ahead of the first pitchers. They are held singly on long stem, generally well above the pitcher traps to avoid the trapping of potential pollinators. The flowers, which depending on species are 3-10 cm in diameter, are dramatic and have an elaborate design which prevents self-pollination. It consists of five sepals superintended by three bracts, numberous anthers, and an umbrella-like five-pointed style, over which five long yellow or red petals dangle. The whole flower is held upside-down, so that the umbrella-like style catches the pollen dropped by the anthers. The stigmata are located at the tips of the umbrella-like style. The primary pollinators are bees. Bees searching for nectar must force their way past one of the stigmas to enter the chamber formed by the style. Inside, they will inevitably come in contact with a lot of pollen, both from the hanging anthers and from the pollen collected by the style. Upon exiting, the bees must force their way under one of the flap-like petals. This keeps them away from the stigma, avoiding self-pollination. The next flower visited receives on its stigmata some of the first flower's pollen, and the cycle continues.

Floral formula: Ca5 Co5 A∞ G(5)

The flowers of almost all species are scented. The scent varies, but is often strong and sometimes unpleasant. S. flava has an especially strong odor resembling cat urine.

Flowers generally last about two weeks. At the end of the flowering period, the petals drop and the ovary, if pollinated, begins to swell. The seed forms in five lobes, with one lobe producing significantly smaller numbers of seeds than the other lobes. On average, 300-600 seed are produced , depending on species and pollination success. Seed takes five months to mature, at which point the seed pod turns brown and splits open, scattering seed. The seeds are 1.5-2 mm in length and have a rough, waxy coat which makes it hydrophobic, possibly for seed dispersal by flowing water.Brittnacher, John; Growing Sarracenia from seed; ICPS website, retrieved 17 May 2006 at 15:53. Sarracenia seed requires a stratification period to germinate. Plants grown from seed start producing functioning traps almost immediately, although they differ in morphology from adult traps for the first year or so, being simpler in structure. Plants require 3-5 years to reach maturity from seed.

Growth cycle

Pitcher production begins at the end of the flowering period in spring, and lasts until late autumn. At the end of autumn, the pitchers begin to wither and the plants produce non-carnivorous leaves called phyllodia, which play a role in the economics of carnivory in these species. Since the supply of insects during winter is decreased, and the onset of cold weather slows plant metabolism and other processes, putting energy into producing carnivorous leaves would be uneconomical for the plant.

Range and habitat

Seven of the eight species are confined to the south-eastern coastal plain of the United States. One species (S. purpurea) continues north well into Canada. The typical habitat is warm-temperate; all Sarracenia are perennial and require a distinct summer and winter. A few subspecies or varieties (Sarracenia rubra ssp. alabamensis, Sarracenia rubra ssp. jonesii or Sarracenia purpurea var. montana) can be found more landinward in mountains (i.e. the Appalachian mountains).

Sarracenia tend to inhabit permanently wet fens, swamps, and grassy plains. These habitats tend to be acidic with soil made up of sand and Sphagnum moss. Frequently, the soil will be poor in nutrients; often continuously washed clean by moving water. The plants gain their advantage from their ability to extract nutrients from insect prey in this mineral-poor environment. The plants prefer strong, direct sunlight with no shade.

In several cases, carnivorous plant enthusiasts have introduced Sarracenia purpurea into suitable habitats outside of its natural range, where it has naturalized. Some of these populations are decades old; the oldest known occurrence in the swiss Jura mountains is about one hundred years old. Beside Switzerland, such naturalized populations can be found in Ireland, England (Lake District), in Middle Franconia in Bavaria, Germany, and in Mendocino County along the California coast.

Environmental status

Sarracenia are threatened in the wild by development and the drainage of their habitat. Estimates indicated that 97.5% of Sarracenia habitat has already been destroyed in the southeastern U.S. Groves, M., ed. 1993. Horticulture, Trade and Conservation of the Genus Sarracenia in the Southeastern States of America: Proceedings of a Meeting Held at the Atlanta Botanical Garden, Sept. 22-23, 1993, 17pp., the home of all but one subspecies of Sarracenia. Currently the biggest threats to surviving populations are urban development, drainage of habitat for forestry, runoff of herbicides from agriculture, fire suppression, cut pitcher trade for floristry, and plant trade. Robbins, C. S. 1998. Examination of the U.S. Pitcher-plant Trade With a Focus on the White-topped Pitcher-plant. Traffic Bulletin. Excerpts, Vol. 17, No. 2 (June 1998) The latter two threaten survival of Sarracenia not only through depletion of healthy population, but also because of the damaging effects (soil compaction and altered moisture levels) of repeated foot and vehicular traffic that comes with harvesting. The Fish and Wildlife Service estimates that approximately 1.6 million pitchers were cut for the domestic market in 1991. U.S. Fish and Wildlife Service. 1991. U.S. CITES Permits and Export Figures for Sarracenia 1990-1991. Washington, DC.

Some protective legislation exists. Several southeastern states, such as Florida, Georgia, and South Carolina, have conservation laws which protect Sarracenia. However, most of the remaining wetlands in the southeastern U.S. lie on private land. Plants on this land are not protected by state legislation. The key states of Alabama and Mississippi have no such legislation at all, so that even plants on public land have no protection. Three Sarracenia have been listed as "Federally Endangered" under the USA Endangered Species Act (1973) — S. rubra subsp. alabamensis (S. alabamensis) in Alabama, S. rubra subsp. jonesii in North and South Carolina, and S. oreophila in Alabama, Georgia and North Carolina. These taxa are also on CITES Appendix I, giving them international protection by making export of wild-collected plants illegal. The other species, while appearing on CITES Appendix II, have little federal protection.

Some efforts have been made to curb the existing threats to plants. In 2003 the nternational Carnivorous Plant Society (ICPS) ran a trial distribution program in which young S. rubra ssp. alabamanensis plants were grown from seed collected from 3 of the 12 known S. alabamanensis sites, and were distributed to members in an attempt to increase availability of this plant in cultivation, with the hopes of thereby decreasing the poaching that was endangering the survival of this taxa in the wild.

In 2004, a number of concerned plant enthusiasts founded the North American Sarracenia Conservancy (NASC), which aims to "serve as a living record of the taxonomic, morphological and genetic diversity of the genus Sarracenia for purposes of conservation and cultivation." The NASC is a grassroots nonprofit organization working to build a genetic Sarracenia bank by overseeing the maintanance of genetic strains from all remaining wild populations in cultivation, with the eventual aim of being able to supply these strains for re-introduction in suitable habitats. A similar but centralized collection exists in the UK, with 2000+ clones representing all species (many with location data) and numerous hybrids currently being housed by Sarracenia expert Mike King. This UK collection is part of the NCCPG National Plant Collection® scheme. While none of these efforts curb the biggest threats - urban development and habitat destruction - they aim to help reduce plant poaching while at the same time making these plants available to future generations.

Classification

For a complete list of subspecies, varieties, and common hybrids, please see separate article List of Sarracenia species and hybrids.

The genus Sarracenia belongs to the family Sarraceniaceae, which also contains the closely allied genera Darlingtonia and Heliamphora. Under the Cronquist system, this family was put in the order Nepenthales along with Nepenthaceae and Droseraceae. The APG II system, however, assigns Sarraceniaceae to the order Ericales and the other two to the order Caryophyllales.

There are generally reckoned to be 8 species of Sarracenia, although this figure is disputed, with some authorities splitting the various subspecies and forms of S. rubra into anything from 3 to 5 true species. The freedom with which Sarracenia species hybridise and produce fertile and viable offspring makes classification based on naïve biological species concepts somewhat fraught. The 8 currently recognized species are:

It was previously the case that many more species were named, due to the ease with which they hybridize. An unusual feature of Sarracenia is that their hybrid offspring are all fertile and able to hybridise further – giving the possibility of hundreds of different hybrids that have multiple species in varying amounts in their ancestry. Since many species ranges overlap, hybrids in the wild were relatively common. As a result, initial classification included many of these hybrids as separate species. Many hybrids of Sarracenia are still commonly referred to by their obsolete species names, particularly in horticulture. These hybrids are all popularly cultivated by carnivorous plant enthusiasts, and there are consequently a huge number of hybrids and cultivars, most bred for showy pitchers. S. × catesbaei is the very common cross between S. flava and S. purpurea. Many of these hybrids occur naturally in the wild.

Several species have subspecies or recognized varieties. The International Carnivorous Plant Society (ICPS) formally recognizes a number of cultivars as well. See the complete list for a listing of species including these taxa.

Currently, S. rubra has five recognized subspecies. However, it is arguably a complex of several species and subspecies (including S. rubra (senso stricto), S. gulfensis, S. wherryi, S. jonesii, and S. alabamensis).

Botanical history

Sarracenia were discovered as early as the 16th century, within a century of Christopher Columbus' discovery of the New World. L'Obel included an illustration of S. minor in his Stirpium Adversaria Nova in 1576. The first description and plate of a Sarracenia to show up in botanical literature was published by Carolus Clusius, who received a partial dried specimen of what was later determined to be S. purpurea subsp. purpurea, publishing it under the name Limonium peregrinum. The exact origins of this specimen remains unknown, as few explorers are known to have collected plant specimens from the range of this subspecies before that time. Cheek and Young suggest that the most likely source is Cartier's expeditions to what is now Quebec between 1534 and 1541. The fragile flowerless specimen that made its way to Clusius 60 years later was enough to excite his interest, but not enough for him to place it among related plants; his closest guess was the wholly unrelated Sea Lavender genus.

The name Sarracenia was first employed by Michel Sarrazin, the Father of Canadian Botany who in the late 17th century sent live specimens of S. purpurea to the Parisian botanist Joseph Pitton de Tournefort, who thereupon described the species. Linnaeus adopted this name when he published his Species Plantarum (1753), using it for the two known species at the time: Sarracenia purpurea and Sarracenia flava. The first successful flowering in culture occurred in 1773. In 1793 William Bartram noted in his book about his travels in the southwest U.S. that numerous insects were caught in the pitchers of these plants, but doubted that any benefit could be derived from them. It wasn't until 1887 that research by Dr. Joseph H Melichamp proved the carnivorous nature of this genus. This finding was supported by a study by J.S. Hepburn, E.Q. St. John and F.M. Jones in 1920Hepburn, J.S., Jones, F.M., and St. John, E.Q. 1920, The absorption of nutrients and allied phenomena in the pitchers of the Sarraceniaceae. J. of the Franklin Inst., 189:147-184.. Extended field surveys and labaratory studies by Dr. Edgar Wherry greatly increased the knowledge of this genus, which as further been extended by the more recent works of Drs. Donald Schnell and Eward Case.

Cultivation

Sarracenia are considered easy to grow and are widely propagated and cultivated by gardeners and carnivorous plant enthusiasts. Several hybrids between the very hardy S. purpurea and showy varieties like S. leucophylla are becoming common in garden centres in North America and Europe.

Sarracenia require constantly moist-wet, nutrient free acidic soil. This is most often achieved with a potting mix consisting of peat moss mixed with sand or perlite. As their roots are sensitive to nutrients and minerals, only pure water, such as distilled, rain, or RO water, can be used to water them. Sarracenia prefer sunny conditions during their growing season but require a dormancy period, with decreased light and temperatures, of a few months in the winter.

Propagation

Sarracenia do not self-pollinate and therefore require hand pollination or access to natural pollinators such as bees. Sarracenia pollen remains potent for several weeks when refrigerated, and so is stored by cultivators and used to pollinate later-flowering species. Given that all Sarracenia hybrids are fertile and will hybridize further, this characteristic allows cultivators to produce a limitless number of variants through hybridization.

The copious seeds produced store well if kept dry. In climates or seasons that cannot provide the cold, damp period of stratification required by the seeds for germination, growers mimic this conidition by placing the seeds in a refridgerator for 4-8 weeks. The seeds are sown on the surface of their substrate and germinate when transferred to warmer, bright conditions. Sarracenia seedlings all look alike for the first two or three years; the plants reach maturity after four or five years.

Mature Sarracenia are commonly propagated by division. Their rhizomes extend and produce new crowns of pitchers over the course of a few growing seasons, and cultivators divide and separate the rhizomes during the plant's winter dormancy or early in the growing season. This technique is also used to separate sections of rhizomes which have no pitchers: when re-potted, the section usually generates a new crown of pitchers. A further technique is employed to encourage new crowns to appear which does not involve division of the rhizome: small notches up to 5 mm deep are cut into the top of the rhizome, whereupon a new crown frequently develops at the site of the notch.

Citations

References

  • Schnell, Donald E.: Carnivorous Plants of the United States and Canada, Portland, 2002, ISBN 0881925403
  • D’Amato, Peter, The Savage Garden, Berkeley 1998, ISBN 0898159156

External links

Sarraceniaceae | Carnivorous plants

Schlauchpflanzen | Sarracénie | サラセニア | Sarracenia

 

This article is licensed under the GNU Free Documentation License. It uses material from the "Sarracenia".

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