Carnivorous plants are found in low-nutrient areas. Also known as insectivorous plants, they trap insects and other small animals and digest them for nitrogen and phosphorous. Essentially, they eat animals.
Taxonomically, carnivorous plants are quite varied. They belong to the Kingdom Plantae and the Division Anthophyta, which consists of flowering plants that are classified as either Monocotyledones or Dicotyledones. Both classes contain carnivorous plants, but most are Dicotyledones. They span many classes, orders, and families, which demonstrates that carnivorous plants have evolved independently multiple times throughout evolutionary history.
Three different methods for trapping prey are demonstrated by three different plants: pitcher plants, Venus flytraps, and sundews.
Insects Cannot Escape the Pitcher Plant Trap
Pitcher plants span many taxonomic orders, but they share one important characteristic: the pitcher. The method of capturing insects is passive, meaning that the plant does nothing to trap its prey.
Pitcher plants are flowering plants with leaves that form cups, or pitchers. Trumpet pitchers have tall tubes for pitchers. According to " The Genus Sarracenia," by the International Carnivorous Plant Society, "The pitchers are brightly colored, and are endowed with sugar-exuding glands called extrafloral nectaries (i.e. nectar sites that are not in flowers). It is significant that the pitcher coloration and distribution of nectaries are usually strongest near the pitcher opening – a dangerous place for incoming insects!"
The pitchers are lined with downward-pointing hairs on the inside to prevent insects from flying out. The slippery, inner surface of the pitcher prevents insects from climbing out, although many ants can escape.
The fluid inside a pitcher is acidic and has a lower surface tension than water. This prevents insects from walking on top of the water, causing them to drown and to be digested by the enzymes in the fluid so that the pitcher can absorb the nutrients from the insect.
Venus Flytrap Leaf Lobes Snap Shut
Whether it is from cartoons or horror movies, Venus flytraps have the reputation of being man-eating plants, but they are much too small for this. They are carnivorous and feed on insects, reptiles, and other small creatures that stimulate the leaves to close – an active trap.
The trap consists of two lobes of a leaf that are lined with tooth-like structures around the edges. Each lobe has two or three hairs. According to Robert J. Brooker, et al., "If a single hair is touched and another touch does not occur soon thereafter, nothing happens. But when a fly or similar prey lands on the leaf and brushes against the same hair twice, or touches a second hair within 20–40 seconds, the leaf lobes snap shut around it."
It generally takes about 10 days to fully digest the animal, after which the trap will reopen. Each trap will last for three or four digestion cycles.
Sundew Traps Insects With a Thick Mucilage
Sundew leaves have hair with glands that secrete a sticky mucilage. An insect that lands on a sundew is immediately trapped by the mucilage. As it moves, it becomes covered with this thick material which coats the breathing pores of the insect. The sundew then rolls up its leaf to enclose the insect for digestion.
Nitrogen-poor environments necessitated the development of carnivorous plants because nitrogen is necessary for the synthesis of important organic materials, such as amino acids. Carnivorous plants lure prey with sweet nectar and brightly-colored leaves. The prey is then stuck to a trap, enclosed by the trap, or unable to fly or climb out of a trap. All of these traps excrete digestive enzymes that break down the prey to be metabolized by the plant.
Reference
Brooker, Robert J., Widmaier, Eric P., Graham, Linda E., and Stiling, Peter D. Biology. New York: McGraw-Hill, 2008.
Glime, Janice M., Grace, Celine E., and Owen, Jackie M. Laboratory Manual for Organismal Biology. Michigan Technological University, 2006.
Diane Ursu - Diane Ursu joined Suite101 as a contributing writer in August 2009 and became a Feature Writer in January 2010. She is a freelance writer ...
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