- Pitcher plant
Pitcher plants are
carnivorous plant s whose prey-trapping mechanism features a deep cavity filled withliquid known as a pitfall trap. It has been widely assumed that the various sorts of pitfall trap evolved from rolled leaves, with selection pressure favouring more deeply cupped leaves overevolution ary time. However, some pitcher plant genera (such as "Nepenthes ") are placed within clades consisting mostly of flypaper traps: this indicates that this view may be too simplistic, and some pitchers may have evolved from flypaper traps by loss ofmucilage .Whatever their evolutionary origins, foraging, flying or crawling
insect s such as flies are attracted to the cavity formed by the cupped leaf, often by visual lures such asanthocyanin pigments, andnectar bribes. The sides of the pitcher are slippery and may be grooved in such a way so as to ensure that the insects cannot climb out. The small bodies of liquid contained within the pitcher traps are calledphytotelmata . They drown the insect, and the body of it is gradually dissolved. This may occur by bacterial action (the bacteria being washed into the pitcher by rainfall) or byenzyme s secreted by the plant itself. Furthermore, some pitcher plants contain mutualistic insectlarva e, which feed on trapped prey, and whoseexcreta the plant absorbs. Fact|date=May 2008 Whatever the mechanism of digestion, the prey items are converted into a solution ofamino acid s,peptide s,phosphate s,ammonium andurea , from which the plant obtains its mineral nutrition (particularlynitrogen andphosphorus ). Like all carnivorous plants, they occur in locations where thesoil is too poor in minerals and/or too acidic for most plants to be able to grow.Types of pitcher plants
The families
Nepenthaceae andSarraceniaceae are the best-known and largest groups of pitcher plants.The Nepenthaceae contains a single
genus , "Nepenthes ", containing about 120 species and numerous hybrids and cultivars. In theseOld World pitcher plants, the pitchers are borne at the end oftendril s that extend from themidrib of an otherwise unexceptional leaf. The plants themselves are often climbers, accessing the canopy of their habitats using the aforementioned tendrils, although others are found on the ground in forest clearings, or asepiphyte s on trees.In contrast, the
New World pitcher plants (Sarraceniaceae), which comprise three genera, are ground-dwelling herbs whose pitchers arise from a horizontalrhizome . In this family, the entire leaf forms the pitcher, whereas in the Nepenthaceae, the pitcher arises from the terminal portion of the leaf. The species of "Heliamphora ", which are popularly known as marsh pitchers (or erroneously as sun pitchers), have a simple rolled-leaf pitcher, at the tip of which is a spoon-like structure that secretes nectar. They are restricted to areas of high rainfall inSouth America . TheNorth America n genus "Sarracenia " are the trumpet pitchers, which have a more complex trap than "Heliamphora", with an operculum, which prevents excess accumulation of rainwater in most of the species. The single species in theCalifornia n genus "Darlingtonia" is popularly known as the cobra plant, due to its possession of an inflated 'lid' with elegant false-exits, and a forked 'tongue', which serves to ferry ants and other prey to the entrance of the pitcher. The species in the genus "Sarracenia" readily hybridise, making their classification a complex matter.There are two other genera of pitcher plants, but both contain just one or two carnivorous species.
The
Cephalotaceae is a monotypic family with but one genus and species, "Cephalotus follicularis". This species has a small (2 to 5 cm) pitcher similar in form to those of "Nepenthes". It occurs in only one location in southwesternAustralia .A few species of bromeliads (
Bromeliaceae ), such as "Brocchinia reducta " and "Catopsis berteroniana " are known or suspected to be carnivorous. Bromeliads are monocots, and given that they all naturally collect water where their leaves meet each other, and that many collect detritus, it is not surprising that a few should have been naturally selected to develop the habit into carnivory by the addition ofwax and downward-pointinghair s.The Purple pitcher plant, "
Sarracenia purpurea ", is the floral emblem of the province ofNewfoundland and Labrador ,Canada .Further reading
* Schnell, Donald (2003). "Carnivorous Plants of the United States and Canada". Second Edition. Timber Press, Oregon, U.S.A.
External links
* [http://www.cpukforum.com/ Carnivorous Plants Enthusiast Forum]
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