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Name : Haris Ismail, Hamza Khan and Shayreyar Khan Class: VI-E School: BSS. Insectivorous Plants
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Name : Haris Ismail, Hamza Khan and Shayreyar Khan Class: VI-E School: BSS
Insectivorous Plants Carnivorous plants are plants that derive some or most of their nutrients (but not energy) 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 bogs and rock outcroppings. Charles Darwin wrote Insectivorous Plants, the first well-known treatise on carnivorous plants, in 1875
Nepenthes mirabilis in flower, growing on a road cut in Palau
The primitive pitchers of Heliamphorachimantensis are an example of pitfall traps.
The leaf of a Droseracapensis bending in response to the trapping of an insect
Roridulagorgonias: a borderline carnivore that gains nutrients from its "prey" via the droppings of a predatory bug
The Venus Flytrap (also Venus's Flytrap or Venus' Flytrap), Dionaeamuscipula, is a carnivorous plant that catches and digests animal prey—mostly insects and arachnids. Its trapping structure is formed by the terminal portion of each of the plant's leaves and is triggered by tiny hairs on their inner surfaces. When an insect or spider crawling along the leaves contacts a hair, the trap closes if a different hair is contacted within twenty seconds of the first strike. The requirement of redundant triggering in this mechanism serves as a safeguard against a waste of energy in trapping objects with no nutritional value.
Pitfall traps Pitfall traps are thought to have evolved independently on at least four occasions. The simplest ones are probably those of Heliamphora, the marsh pitcher plant. In this genus, the traps are clearly derived evolutionarily from a simple rolled leaf whose margins have sealed together. These plants live in areas of high rainfall in South America such as Mount Roraima and consequently have a problem ensuring their pitchers do not overflow. To counteract this problem, natural selection has favoured the evolution of an overflow similar to that of a bathroom sink—a small gap in the zipped-up leaf margins allows excess water to flow out of the pitcher. Heliamphora is a member of the Sarraceniaceae, a New World family in the order Ericales (heathers and allies). Heliamphora is limited to South America, but the family contains two other genera, Sarracenia and Darlingtonia, which are endemic to the Southeastern United States (with the exception of one species) and California respectively. Sarraceniapurpurea subsp. purpurea (the northern pitcher plant) can be found as far north as Canada. Sarracenia is the pitcher plant genus most commonly encountered in cultivation, because it is relatively hardy and easy to grow.
Flypaper Traps The flypaper trap is based on a sticky mucilage, or glue. The leaf of flypaper traps is studded with mucilage-secreting glands, which may be short and nondescript (like those of the butterworts), or long and mobile (like those of many sundews). Flypapers have evolved independently at least five times. In the genus Pinguicula, the mucilage glands are quite short (sessile), and the leaf, while shiny (giving the genus its common name of 'butterwort'), does not appear carnivorous. However, this belies the fact that the leaf is an extremely effective trap of small flying insects (such as fungus gnats), and its surface responds to prey by relatively rapid growth. This thigmotropic growth may involve rolling of the leaf blade (to prevent rain from splashing the prey off the leaf surface) or dishing of the surface under the prey to form a shallow digestive pit. The sundew genus (Drosera) consists of over 100 species of active flypapers whose mucilage glands are borne at the end of long tentacles, which frequently grow fast enough in response to prey (thigmotropism) to aid the trapping process. The tentacles of D. burmanii can bend 180° in a minute or so. Sundews are extremely cosmopolitan and are found on all the continents except the Antarctic mainland. They are most diverse in Australia, the home to the large subgroup of pygmy sundews such as D. pygmaea and to a number of tuberous sundews such as D. peltata, which form tubers that aestivate during the dry summer months. These species are so dependent on insect sources of nitrogen that they generally lack the enzyme nitrate reductase, which most plants require to assimilate soil-borne nitrate into organic forms.
The only two active snap traps—the Venus flytrap (Dionaeamuscipula) and the waterwheel plant (Aldrovandavesiculosa)—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.[8] 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 Dionaeamuscipula, 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 themembranes of cells at the base of the trigger hair open, generating an action potential that propagates to cells in the midrib.[9] 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.[10] 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,[9] flipping rapidly from convex to concave[11] 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.
bibliography http://en.wikipedia.org/wiki/Carnivorous_plant
