Carnivorous plant

Nurseryman Nigel Hewitt-Cooper, from West Pennard, was inspecting his tropical garden when he discovered one of his pitcher plants had trapped the bird.He said he was "absolutely staggered" to find it had caught the creature.It is believed to be only the second time such a carnivorous plant has been documented eating a bird anywhere in the world."I've got a friend who's studied these particular plants extensively in the wild and he's never found evidence of any of them having caught birds," said Mr Hewitt-Cooper."The other documented time was in Germany a few years ago and that was in cultivation, not in the wild.

'Become wedged'

"The larger ones frequently take frogs, lizards and mice, and the biggest ones have been found with rats in them, but to find a bird in one is pretty unusual."

The pitcher plant is a genus of Nepenthes from South East Asia which attracts and traps insects in a pool of liquid which it then digests.

Mr Hewitt-Cooper said he thought the great tit had been attracted to the plant on Saturday by the insects and landed on its leaf.

"I think it must have leant in to pluck out an insect that was floating on the fluid inside, tipped in too far and become wedged and unable to get out."

Mr Hewitt-Cooper has been growing carnivorous plants such as pitcher plants, Venus fly traps and sundews for 30 years, and has won several gold medals at the Chelsea Flower Show.

Fatal Attraction

A hungry fly darts through the pines in North Carolina. Drawn by what seems like the scent of nectar from a flowerlike patch of scarlet on the ground, the fly lands on the fleshy pad of a ruddy leaf. It takes a sip of the sweet liquid oozing from the leaf, brushing a leg against one tiny hair on its surface, then another. Suddenly the fly's world has walls around it. The two sides of the leaf are closing against each other, spines along its edges interlocking like the teeth of a jaw trap. As the fly struggles to escape, the trap squeezes shut. Now, instead of offering sweet nectar, the leaf unleashes enzymes that eat away at the fly's innards, gradually turning them into goo. The fly has suffered the ultimate indignity for an animal: It has been killed by a plant.

Snap traps

The only two active snap traps—the Venus flytrap (Dionaea muscipula) and the waterwheel plant (Aldrovanda vesiculosa)—are believed to have had a common ancestor with similar adaptations. Their trapping mechanism has also been described as a "mouse trap", "bear trap" or "man trap", based on their shape and rapid movement. However, the term snap trap is preferred as other designations are misleading, particularly with respect to the intended prey. Aldrovanda is aquatic and specialised in catching small invertebrates; Dionaea is terrestrial and catches a variety of arthropods, including spiders.

The traps are very similar, with leaves whose terminal section is divided into two lobes, hinged along the midrib. Trigger hairs (three on each lobe in Dionaea muscipula, many more in the case of Aldrovanda) inside the trap lobes are sensitive to touch. When a trigger hair is bent, stretch-gated ion channels in the membranes of cells at the base of the trigger hair open, generating an action potential that propagates to cells in the midrib.These cells respond by pumping out ions, which may either cause water to follow by osmosis (collapsing the cells in the midrib) or cause rapid acid growth.The mechanism is still debated, but in any case, changes in the shape of cells in the midrib allow the lobes, held under tension, to snap shut flipping rapidly from convex to concave[15] and interring the prey. This whole process takes less than a second. In the Venus flytrap, closure in response to raindrops and blown-in debris is prevented by the leaves having a simple memory: for the lobes to shut, two stimuli are required, 0.5 to 30 seconds apart.[citation needed]

The snapping of the leaves is a case of thigmonasty (undirected movement in response to touch). Further stimulation of the lobe's internal surfaces by the struggling insects causes the lobes to close even tighter (thigmotropism), sealing the lobes hermetically and forming a stomach in which digestion occurs over a period of one to two weeks. Leaves can be reused three or four times before they become unresponsive to stimulation, depending on the growing conditions.

Bladder traps

Bladder traps are exclusive to the genus Utricularia, or bladderworts. The bladders (vesicula) pump ions out of their interiors. Water follows by osmosis, generating a partial vacuum inside the bladder. The bladder has a small opening, sealed by a hinged door. In aquatic species, the door has a pair of long trigger hairs. Aquatic invertebrates such as Daphnia touch these hairs and deform the door by lever action, releasing the vacuum. The invertebrate is sucked into the bladder, where it is digested. Many species of Utricularia (such as U. sandersonii) are terrestrial, growing on waterlogged soil, and their trapping mechanism is triggered in a slightly different manner. Bladderworts lack roots, but terrestrial species have anchoring stems that resemble roots. Temperate aquatic bladderworts generally die back to a resting turion during the winter months, and U. macrorhiza appears to regulate the number of bladders it bears in response to the prevailing nutrient content of its habitat.

Borderline carnivores


To be a fully fledged carnivore, a plant must attract, kill, and digest prey;and it must benefit from absorbing the products of the digestion (mostly amino acids and ammonium ions).To many horticulturalists, these distinctions are a matter of taste. There is a spectrum of carnivory found in plants: from completely non-carnivorous plants like cabbages, to borderline carnivores, to unspecialised and simple traps, like Heliamphora, to extremely specialised and complex traps, like that of the Venus flytrap.

The borderline carnivores include Roridula and Catopsis berteroniana. Catopsis is a borderline carnivorous bromeliad, like Brocchinia reducta. However, unlike B. reducta, which produces the enzyme phosphatase, C. berteroniana has not been shown to produce any digestive enzymes at all.In these pitfall traps, prey simply fall into the urn, assisted by the waxy scales located on the rim. Roridula has a more intricate relationship with its prey. The plants in this genus produce sticky leaves with resin-tipped glands and look extremely similar to some of the larger sundews. However, they do not directly benefit from the insects they catch. Instead, they form a mutualistic symbiosis with species of assassin bug (genus Pameridea), which eat the trapped insects. The plant benefits from the nutrients in the bugs' faeces. A number of species in the Martyniaceae (previously Pedaliaceae), such as Ibicella lutea, have sticky leaves that trap insects. However, these plants have not been shown conclusively to be carnivorous.Likewise, the seeds of Shepherd's Purse,urns of Paepalanthus bromelioides bracts of Passiflora foetida and flower stalks and sepals of triggerplants (Stylidium) appear to trap and kill insects, but their classification as carnivores is contentious.
The production of specific prey-digesting enzymes (proteases, ribonucleases, phosphatases, etc.) is sometimes used as a criterion for carnivory. However, this would probably discount Heliamphora and Darlingtonia both of which appear to rely on the enzymes of symbiotic bacteria to break down their prey but are generally considered as carnivores. However, discounting the enzyme-based definition leaves open the question of Roridula.