Classification and Range
Tropical pitcher plants belong to a very unique group of flowering plants that have special adaptations found in few other plants: pitcher-shaped leaves which trap and digest small organisms. There are approximately 76 species of tropical pitcher plants, all of which are classified in the genus Nepenthes. The genus Nepenthes comprises its own family, the Nepenthaceae, based on floral and other physical characteristics of these plants.
Tropical pitcher plants of the genus Nepenthes are distributed in tropical areas of northern Australia, southeast Asia, southern China, India and Madagascar.
These plants grow as vines, in the undergrowth, or up in the canopy of tropical forests.
Tropical pitcher plants generally grow as vines, climbing over other plants, and may grow as epiphytes, growing on other plants in the forest canopy, or as low shrubs. The pitchers of tropical pitcher plants may resemble flowers, but are actually modified leaf blades that hang from coiled tendrils. The pitchers are usually shaped like tubes or, as the name implies, like small pitchers. All species in the genus Nepenthes use their pitchers to trap and digest small invertebrate animals.
The pitchers can vary in shape even within the same species of plant depending on the age of the plant, the amount of light, and whether the pitcher is growing near the ground or high up. The pitchers are filled with acidic digestive liquids. The pitchers are able to break down and absorb nutrients from animals, usually invertebrates such as insects, that fall into the pitchers. The pitchers are covered by small lids as they grow, in order to prevent the digestive liquid from being diluted by rainwater. The lids shrivel or open up when the pitchers are fully developed.
There are estimated to be approximately 76 species of Nepenthes in the world. All species of Nepenthes are listed on Appendix II to the Convention on International Trade of Endangered Species of Flora and Fauna (CITES), which restricts trade of these plants. The World Conservation Union (IUCN) lists three species of Nepenthes, all native to Borneo, as endangered. Tropical pitcher plants suffer mainly from habitat destruction, but due to the low numbers of their populations, collecting has also had serious impacts. The incidence of illegal trade in Nepenthes is high. Methods have been developed to produce Nepenthes plants from tissue culture. The horticultural use of plants produced by this process can help reduce the impact on wild Nepenthes. Woodland Park Zoo displays species of Nepenthes in the canopy dome of the Tropical Rain Forest. However, these plants produce pitchers only occasionally depending on seasonal variations of the weather.
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