DK Science: Carnivorous Plants
Meat-eating, or carnivorous, plants can trap and digest insects and other small animals. They do this to obtain the vital nitrogen that they need to grow. Most plants absorb enough nitrogen from nitrates in the soil. Carnivorous plants live in bogs, where nitrates are in short supply, so they need to obtain their nitrogen by digesting prey instead. Carnivorous plants have developed unique ways to catch insects, such as fluid-filled PITCHERS and spring-loaded traps.
The Venus flytrap’s leaves are hinged so that they can snap shut. Sensitive trigger hairs detect any insect that lands on the surface of an open leaf. At the slightest movement, the two halves of the leaf spring shut. As the sides of the trap close around the victim, the plant releases digestive juices. These break down the soft parts of the insect.
Sundews are small bog plants that have hair-covered leaves. They produce a droplet of sticky “dew” at the tip of each hair. Insects are attracted to the fluid, but become stuck. Next, the hairs slowly bend inwards until the whole leaf has folded over the insect. Chemicals released from the hairs digest the insect’s body, and nutrients are taken into the plant.
The pitcher plant is named for the juglike traps that hang below its leaves or grow up from the ground. Each trap has its own lid to keep off the rain and contains special fluid at the bottom. Insects are attracted by the trap’s red markings and the sweet nectar produced around its rim. If the insect lands to drink the nectar, it slips and falls into the trap. It drowns in the fluid at the bottom and its nutrients are slowly absorbed by the plant.
An insect body has to be broken down before its nutrients can be absorbed into the plant. Carnivorous plants such as pitchers use enzymes, similar to the ones that break down food in an animal’s gut. Acids help the enzymes to break down the body. A pitcher plant can digest a small insect within a few hours, but larger ones take days.