The Nepenthes–Carvivorous Pitcher Plants

Nepenthes hamata

The Nepenthes are a genus of pitcher plants which live in tropical forests of the old world.  The carnivorous plants occur in a vast range which stretches from South China to Australia, and from the Philippines, to Madagascar, however the greatest diversity of nepenthes plants is found in Borneo and Sumatra.  Although some of these plants are found in environments where it is always hot or always cold, the majority of Nepenthe species live on tropical mountain slopes where it is hot during the day and cool at night.  They also tend to grow in nutrient-poor soils where they face stiff competition from ultra-competitive tropical trees, vines, and flowers.

Nepenthes ventricosa

In order to produce the nutrients they need (mostly nitrogen and phosphorus) nepenthes have evolved an ingenious solution: they capture small animals inside elegant cup-like traps and digest them as fertilizer. To attract prey, nepenthes produce sugary nectars, sweet perfumes, and vibrant colors. Pitcher plants usually trap insects and other small arthropods, however the very largest of these plants can catch lizards, frogs, rodents, and even birds.

A large nepenthe slowly digests an unhappy rat (from Redfern Natural History)

The traps of pitcher plants are highly modified leaves (which sometimes have lid-like operculums to keep rain out).  At the bottom of each trap is a pool of fluid containing compounds which prevent the prey from escaping.  In some cases biopolymers make the trap extremely sticky/syrupy, however in other cases the liquid at the bottom of pitcher plants seems watery (although it still has an effect on insects and myriapoda).  The lip of the nepenthe plant is extremely slippery and the waxy throat prevents the plant’s victims from clambering out.

Nepenthes attenboroughii

The name of the nepenthe might be the most sinister thing about this sinister plant.  In the Odyssey (and other classical Greek sources), nepenthe was a magical fluid which erased cares and worries completely from the mind.  The nepenthe does remove all worries from small guests who come to call on it—albeit by killing them and digesting their bodies.

Nepenthes izumiae

Unfortunately many nepenthes are threatened by habitat loss (particularly as the great rainforests around the Indian Ocean are destroyed by loggers and farmers). Fortunately human beings are fond of nepenthes (partly because of our shared nature and partly because of the plants’ racy good looks) and fanciers produce great moist greenhouses of beautiful malicious hybrids.

A fancy hybrid nepenthe

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