Carnivorous plants (also known as insectivorous plants) derive their nutrients from attracting, trapping and eating insects and arthropods (a distinct species of insects, crustaceans and arachnids); one of the reasons plants have evolved to be carnivorous is that they grow in habitats where there are very few nutrients to be found in the soil.
There are more than twelve genera of carnivorous plants in five botanical families; these include approximately 625 species which attract, trap and eat the nutrients of their prey. In addition, there are over 300 protocarnivorous plant species which trap their prey but do not have the ability to absorb the nutrients of their prey.
Where are Carnivorous Plants Found?
Carnivorous plants are usually found in areas where other plants are not, that is in low-nutrient environments. Carnivorous plants grow in bogs and swamps, standing waters and minimal flow streams, sandy and rocky sites (rock faces, plateaus and mountain slopes and cliffs) and forests; there are many species of carnivorous plants located throughout the world in Europe, Asia, Africa, Australia and the Americas.
Species of Carnivorous Plants
Species of carnivorous plants include:
- Australia and Asia – the Australian Pitcher Plant (Cephalotus follicularis) and the endemic Pitcher Plant found in Asia (Nepenthes madagaascariensis).
- North America – the Cobra Lily (Darlingtonia californica) and the Saracenia species.
- Europe - Sundew (Drosera rotundifolia, Drosera intermedia, Drosera anglica)and the Butterwort (Pinguicula vulgaris).
- Africa – the Hookleaf (Triphyophyllum peltatum).
How Do Carnivorous Plants Attract Insects?
In the first instance, carnivorous plants need to attract insects. Many carnivorous plants have developed sophisticated mechanisms with which to attract and trap insects; these include tactile, olfactory and optical devices. Some carnivorous plants have brightly colored, attractive 'decoy' flowers to attract insects for pollination; the insect is attracted to the 'flower' which is, in fact, a trap.
The trap systems of some carnivorous plants emit ultraviolet color patterns, as in the case of real flowers, and the insect is again fooled into believing it is pollinating a flower; the Venus Flytrap (Dionaea muscipula) is an example of this type of carnivorous plant. Some insects are capable of detecting smell; in order to attract these insects species of carnivorous plants, such as the Nepenthes, emit a sweet smell which mimics that of nectar.
How Do Carnivorous Plants Trap Insects?
Carnivorous plants actually trap insects via the leaf organs and not the flower (a common misconception). Types of traps include snap traps, snare traps, adhesive traps, pitfall traps and suction traps. These traps work in various ways depending on the species of carnivorous plant; for example, Sundews (Drosera spp.) and Butterworts (Pinguicula vulgaris) have adhesive traps whereas the Venus Flytrap (Dionaea muscipula) has a snap trap.
How Do Carnivorous Plants Digest Insects?
Once an insect has been successfully trapped by a carnivorous plant, the plant must 'digest' the insect to absorb the nutrients it requires; in order to do this, carnivorous plants produce enzymes which initiate a chemical reaction. Enzymes are located in the digestive glands of carnivorous plants and are classified into three groups – stalked glands, sessile glands and sunken glands. Different species of carnivorous plants digest in various time frames; in some carnivorous species, it can take days, if not weeks, to digest an insect.
How Do Carnivorous Plants Use The Nutrients From An Insect?
The absorbed nutrients from the digestion process of the insect are transported to various parts of the plant including reproductive organs and new tissue to maintain the growth and life of the plant. Carnivorous plants do not absorb all the nutrients available from an insect and only absorb what they need; for example, Sarracenia plants only absorb nitrogen and phosphorous in large quantities.
References:
Barthlott, Wilhelm, Porembski, Stefan, Seine, Rudiger, Theisen, Inge 2007 The Curious World of Carnivorous Plants USA: Timber Press
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