Pitcher plant (Nepenthes boschiana)
|Size||Height: up to 5m (2)|
Pitcher height: 20 cm (2)
Classified as Endangered (EN) on the IUCN Red List 2007 (1) and listed on Appendix II of CITES (3)
This impressive carnivorous plant belongs to a spectacular family of tropical Asian pitcher plants (Nepenthes species). Nepenthes boschiana is a vine, which climbs to a height of about five metres and has modified pitcher-shaped leaves which hang from coiled tendrils. Nepenthes species usually have two or three different types of pitcher, generally known as upper and lower pitchers (4). The trumpet-shaped pitchers of Nepenthes boschiana vary in colour from white to red (2), and contain an acidic fluid, secreted by the many glands which cover the inside surface of the lower half of the pitcher (4). The smooth and waxy upper inner surface of the pitcher makes it impossible for insects that fall into the pitchers to gain a foothold (4), and a ridge of hardened tissue lining the mouth of the pitcher, the peristome, bears downward pointing teeth, also preventing insects from escaping (2). A lid overhangs the mouth of the pitcher preventing rain water from diluting the pitcher fluid (2). When young, Nepenthes boschiana, is covered in brown and white hairs, but is either hairless or sparsely covered with short white hairs when mature (2).
Found only on the uppermost ridges of Mount Besar and Mount Sakoembang, Borneo, Indonesia, at altitudes between 900 and 1,880 metres (2) (5).
Nepenthes boschiana grows on limestone amongst stunted vegetation, along the uppermost ridges of Mount Besar and Mount Sakoembang (2).
Pitcher plants are dioecious meaning that male and female flowers grow on separate plants (4), and only begin to flower once the upper pitchers are produced (5). The flowers produce large amounts of nectar during the early evening and night, which evaporates by morning. This nectar attracts flies during the early evening and moths at night to aid pollination. Once fertilised, a fruit usually takes about three months to develop and ripen. The fruits of Nepenthes species produce between 100 and 500 very light, winged seeds, which can measure up to 30 millimetres long, and are thought to be dispersed by the wind (2) (6). Despite enormous numbers of seeds being produced, only a few manage to germinate and only a fraction of those survive to maturity (2).
Carnivorous pitcher plants are adapted to grow in soils low in nutrients. Although the plants do gain some nutrition through the soil, and energy through photosynthesis, they supplement this with a diet of invertebrates, usually consisting of ants, cockroaches, centipedes, flies and beetles (4). Insects are attracted to the pitchers by their bright colours and nectar, which is secreted by glands situated on the lid and the peristome of the pitcher. The insects fall into the acidic fluid at the base of the pitcher and, unable to escape, they drown. Digestive enzymes are then released to break down the captured prey (4).
Despite the hostile environment of the pitchers, they can be home to number of animals. The red crab spider (Misumenops nepenthicola) inhabits pitcher plants in Malaysia, Singapore and Indonesia including some species in Borneo. This spider ambushes insects that crawl into the pitcher, and preys upon other insects, such as mosquitoes, as they emerge from larvae that live in the pitcher fluid (2).
Nepenthes species are threatened by a combination of over-collection and habitat loss (2). In Indonesia, habitat destruction is a major problem as a result of illegal and commercial logging and large agricultural projects such as rubber and oil palm plantations (7). Nepenthes boschiana is not found in any national park or protected area (8), and has a highly localised distribution making this species particularly susceptible to extinction through habitat destruction or catastrophic environmental events, such as drought or fire. In addition, montane species, such as Nepenthes boschiana, take longer to recover than lowland plants after such events as growth is slower (2).
Although listed under Appendix II of the Convention on International Trade in Endangered Species (CITES) which limits the international export of this species (3), trade is very difficult to regulate. There is no requirement for internationally traded Nepenthes to be identified down to species level and plants simply labelled as Nepenthes accounted for 94 percent of all exported Nepenthes plants between 1988 and 1993. This needs to be remedied and urgent attention is required to close other trade loopholes (2). Nepenthes species, including Nepenthes boschiana, are being increasingly cultivated, helping to reduce the impact on wild populations. Conservation efforts can be made more effective not only by the implementation and enforcement of protective laws, but also by the encouragement of artificial propagation and establishment of habitat reserves (8).
For more information on Nepenthes species see:
- Clarke, C. (1997) Nepenthes of Borneo. NaturalHistory Publications, Kota Kinabalu, Malaysia.
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- Carnivore: flesh-eating.
- Enzymes: Proteins that trigger, or accelerate, activity in the cells of the body, for example, breaking down foods during digestion, and building new proteins.
- Fertilisation: in a flowering plant, fertilisation is the process of a pollen grain joining with the ovule (female egg cell). After fertilisation, the female parts of the flower develop into a fruit.
- Invertebrates: animals with no backbone.
- Larvae: stage in an animal’s lifecycle after it hatches from the egg. Larvae are typically very different in appearance to adults; they are able to feed and move around but usually are unable to reproduce.
- Photosynthesis: metabolic process characteristic of plants in which carbon dioxide is broken down, using energy from sunlight absorbed by the green pigment chlorophyll. Organic compounds are made and oxygen is given off as a by-product.
- Pollination: the transfer of pollen grains from the stamen (male part of a flower) to the stigma (female part of a flower) of a flowering plant. This usually leads to fertilisation, the development of seeds and, eventually, a new plant.
- Rhizome: thickened, branching, creeping storage stems. Although most rhizomes grow laterally just along or slightly below the soil's surface, some grow several inches deep. Roots grow from the underside of the rhizome, and during the growing season new growth sprouts from buds along the top. A familiar rhizome is the ginger used in cooking.
IUCN Red List (December, 2009)