Pitcher plants are
carnivorous plantCarnivorous plants are plants that derive some or most of their nutrients from trapping and consuming animals or protozoans, typically insects and other arthropods. Carnivorous plants appear adapted to grow in places where the soil is thin or poor in nutrients, especially nitrogen, such as acidic...
s whose prey-trapping mechanism features a deep cavity filled with
liquidLiquid is one of the three classical states of matter . Like a gas, a liquid is able to flow and take the shape of a container. Some liquids resist compression, while others can be compressed. Unlike a gas, a liquid does not disperse to fill every space of a container, and maintains a fairly...
known as a
pitfall trap. It has been widely assumed that the various sorts of pitfall trap evolved from rolled leaves, with
selectionNatural selection is the nonrandom process by which biologic traits become either more or less common in a population as a function of differential reproduction of their bearers. It is a key mechanism of evolution....
pressure favouring more deeply cupped leaves over
evolutionEvolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...
ary time. However, some pitcher plant
generaIn biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
(such as
NepenthesThe Nepenthes , popularly known as tropical pitcher plants or monkey cups, are a genus of carnivorous plants in the monotypic family Nepenthaceae. The genus comprises roughly 130 species, numerous natural and many cultivated hybrids...
) are placed within
cladesCladistics is a method of classifying species of organisms into groups called clades, which consist of an ancestor organism and all its descendants . For example, birds, dinosaurs, crocodiles, and all descendants of their most recent common ancestor form a clade...
consisting mostly of flypaper traps: this indicates that this view may be too simplistic, and some pitchers may have evolved from the common ancestors of today's flypaper traps by loss of
mucilageMucilage is a thick, gluey substance produced by most plants and some microorganisms. It is a polar glycoprotein and an exopolysaccharide.It occurs in various parts of nearly all classes of plant, usually in relatively small percentages, and is frequently associated with other substances, such as...
.
Whatever their evolutionary origins, foraging, flying or crawling
insectInsects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
s such as flies are attracted to the cavity formed by the cupped leaf, often by visual lures such as
anthocyaninAnthocyanins are water-soluble vacuolar pigments that may appear red, purple, or blue according to pH...
pigments, and nectar 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 called
phytotelmataPhytotelma is a term for water bodies held by plants. The water accumulated on these plants may serve as substratum for associated fauna, and often the fauna associated with phytotelmata is unique....
. 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 by
enzymeEnzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
s secreted by the plant itself. Furthermore, some pitcher plants contain mutualistic insect
larvaA larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...
e, which feed on trapped prey, and whose excreta the plant absorbs. Whatever the mechanism of digestion, the prey items are converted into a solution of
amino acidAmino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...
s,
peptidePeptides are short polymers of amino acid monomers linked by peptide bonds. They are distinguished from proteins on the basis of size, typically containing less than 50 monomer units. The shortest peptides are dipeptides, consisting of two amino acids joined by a single peptide bond...
s,
phosphateA phosphate, an inorganic chemical, is a salt of phosphoric acid. In organic chemistry, a phosphate, or organophosphate, is an ester of phosphoric acid. Organic phosphates are important in biochemistry and biogeochemistry or ecology. Inorganic phosphates are mined to obtain phosphorus for use in...
s,
ammoniumThe ammonium cation is a positively charged polyatomic cation with the chemical formula NH. It is formed by the protonation of ammonia...
and
ureaUrea or carbamide is an organic compound with the chemical formula CO2. The molecule has two —NH2 groups joined by a carbonyl functional group....
, from which the plant obtains its mineral nutrition (particularly
nitrogenNitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...
and
phosphorusPhosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...
). Like all carnivorous plants, they grow in locations where the
soilSoil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...
is too poor in minerals and/or too acidic for most plants to survive.
Types of pitcher plants
The families Nepenthaceae and
SarraceniaceaeSarraceniaceae is a family of pitcher plants , belonging to order Ericales .The family comprises three extant genera: Sarracenia , Darlingtonia , and Heliamphora . The extinct Archaeamphora longicervia may also belong to this family...
are the best-known and largest groups of pitcher plants.
The Nepenthaceae contains a single
genusIn biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
,
NepenthesThe Nepenthes , popularly known as tropical pitcher plants or monkey cups, are a genus of carnivorous plants in the monotypic family Nepenthaceae. The genus comprises roughly 130 species, numerous natural and many cultivated hybrids...
, containing about 130 species and numerous hybrids and cultivars. In these
Old WorldThe Old World consists of those parts of the world known to classical antiquity and the European Middle Ages. It is used in the context of, and contrast with, the "New World" ....
pitcher plants, the pitchers are borne at the end of
tendrilIn botany, a tendril is a specialized stem, leaf or petiole with a threadlike shape that is used by climbing plants for support, attachment and cellular invasion by parasitic plants, generally by twining around suitable hosts. They do not have a lamina or blade, but they can photosynthesize...
s that extend from the midrib of an otherwise unexceptional leaf. The plants themselves are often climbers, accessing the
canopyIn biology, the canopy is the aboveground portion of a plant community or crop, formed by plant crowns.For forests, canopy also refers to the upper layer or habitat zone, formed by mature tree crowns and including other biological organisms .Sometimes the term canopy is used to refer to the extent...
of their
habitatsA habitat is an ecological or environmental area that is inhabited by a particular species of animal, plant or other type of organism...
using the aforementioned tendrils, although others are found on the ground in forest clearings, or as
epiphyteAn epiphyte is a plant that grows upon another plant non-parasitically or sometimes upon some other object , derives its moisture and nutrients from the air and rain and sometimes from debris accumulating around it, and is found in the temperate zone and in the...
s on trees.
In contrast, the
New WorldThe New World is one of the names used for the Western Hemisphere, specifically America and sometimes Oceania . The term originated in the late 15th century, when America had been recently discovered by European explorers, expanding the geographical horizon of the people of the European middle...
pitcher plants (Sarraceniaceae), which comprise three genera, are ground-dwelling herbs whose pitchers arise from a horizontal
rhizomeIn botany and dendrology, a rhizome is a characteristically horizontal stem of a plant that is usually found underground, often sending out roots and shoots from its nodes...
. 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
HeliamphoraThe genus Heliamphora contains 23 species of pitcher plants endemic to South America. The species are collectively known as sun pitchers, based on the mistaken notion that the heli of Heliamphora is from the Greek helios, meaning "sun"...
, 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 in
South AmericaSouth America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
. The
North AmericaNorth America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
n genus
SarraceniaSarracenia is a genus comprising 8 to 11 species of North American pitcher plants. The genus belongs to the family Sarraceniaceae, which also contain the closely allied genera Darlingtonia and Heliamphora....
are the trumpet pitchers, which have a more complex trap than
Heliamphora, with an
operculumAn operculum, in botany, is a term generally used to describe a structure within a plant, moss, or fungus acting as a cap, flap, or lid. In plants, it may also be called a bud cap.Examples of structures identified as opercula include:...
, which prevents excess accumulation of rainwater in most of the species. The single species in the
CaliforniaCalifornia is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
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 families 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 follicularisCephalotus is a genus which contains one species, Cephalotus follicularis, a small carnivorous pitcher plant. The pit-fall traps of the modified leaves have inspired the common names for this plant, which include Albany Pitcher Plant, Western Australian Pitcher Plant, fly-catcher plant or...
. This species has a small (2–5 cm) pitcher similar in form to those of
Nepenthes. It occurs in only one location in southwestern
AustraliaAustralia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
.
A few species of bromeliads (
BromeliaceaeBromeliaceae is a family of monocot flowering plants of around 3,170 species native mainly to the tropical Americas, with a few species found in the American subtropics and one in tropical west Africa, Pitcairnia feliciana...
), such as
Brocchinia reductaBrocchinia reducta is one of few carnivorous bromeliads. It is native to southern Venezuela, Brazil and Guyana, and is found in nutrient-poor soil....
and
Catopsis berteronianaCatopsis berteroniana is an epiphytic bromeliad thought to be a possible carnivorous plant, similar to Brocchinia reducta, although the evidence is equivocal. Its native range is from southern Florida to southern Brazil. It generally grows on the unshaded twigs of trees, and appears to trap more...
, are known or suspected to be carnivorous. Bromeliads are
monocotsMonocotyledons, also known as monocots, are one of two major groups of flowering plants that are traditionally recognized, the other being dicotyledons, or dicots. Monocot seedlings typically have one cotyledon , in contrast to the two cotyledons typical of dicots...
, 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 selectedNatural selection is the nonrandom process by which biologic traits become either more or less common in a population as a function of differential reproduction of their bearers. It is a key mechanism of evolution....
to develop the habit into carnivory by the addition of
waxthumb|right|[[Cetyl palmitate]], a typical wax ester.Wax refers to a class of chemical compounds that are plastic near ambient temperatures. Characteristically, they melt above 45 °C to give a low viscosity liquid. Waxes are insoluble in water but soluble in organic, nonpolar solvents...
and downward-pointing
hairHair is a filamentous biomaterial, that grows from follicles found in the dermis. Found exclusively in mammals, hair is one of the defining characteristics of the mammalian class....
s.
The Purple pitcher plant,
Sarracenia purpureaSarracenia purpurea, commonly known as the purple pitcher plant, northern pitcher plant, or side-saddle flower, is a carnivorous plant in the family Sarraceniaceae...
, is the floral emblem of the province of
Newfoundland and LabradorNewfoundland and Labrador is the easternmost province of Canada. Situated in the country's Atlantic region, it incorporates the island of Newfoundland and mainland Labrador with a combined area of . As of April 2011, the province's estimated population is 508,400...
,
CanadaCanada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
.
Further reading
- Juniper, B.E., R.J. Robins & D.M. Joel (1989). The Carnivorous Plants. Academic Press, London.
- Schnell, D. (2003). Carnivorous Plants of the United States and Canada. Second Edition. Timber Press, Oregon, U.S.A.