Carnivorous plants have evolved into one of nature's efficient predators. They consume insects and small amphibians. Carnivorous plants require fresh prey to fulfill their nitrogen needs for photosynthesis. They are divided into two categories: active trappers and passive trappers. Active trappers physically trap their prey with modified leaves that close when touched. Passive trappers use a variety of methods, including secreting a sticky residue that acts like fly tape.
The Venus fly trap is an active trapper with modified leaves that trap its prey. Trigger hairs line the interior of its leaves. When prey lands on the leaves, the trigger hairs signal the leaves to snap shut, snaring the prey. Pitcher plants are divided into two groups based on their native locations: American and tropical. Both form tall, pitcher-shaped leaves. Pitcher plants are passive trappers; the bottom of the pitcher fills with a liquid produced by the plants. Some species have smooth interior leaves that prevent prey from crawling back out; other species have small specialized hairs that push prey down into the liquid.
Bladderworts are passive trappers. Their leaves have developed into small bladder-like shapes with trap doors. Bladderworts have trigger hairs similar to those in a Venus fly trap; however, they do not trigger movement of the leaf itself. Rather, they open the trap door.
Sundews are an active trapper. They have tentacle-hair-like structures that excrete a thick, sticky liquid. As their prey struggles, the tentacles wrap tighter around the body of the insect, pulling it in.
Carnivorous plants grow in wet, acidic soils in various regions of the world. Most prefer bogs that are made up of nutrient-deficient peat soils; some prefer a symbiotic relationship with other plants and a few are epiphytes. Epiphytes use other plants for support but form neither a symbiotic or parasitic relationship. Venus fly traps are native to the coastal plains of North and South Carolina.
American pitcher plants range from the Eastern Seaboard to the Upper Midwest of the Unites States; a few species thrive in Canada. Tropical pitcher plants thrive in tropical regions, as their name suggests. There are two groups of tropical pitcher plants: one prefers high mountainous regions that offer cool nights, and another group prefers lowland tropical areas that stay hot and humid day and night. Sundews grow in tropical and temperate regions on every continent in the world. Bladderworts are found growing in bogs and in small ponds. Over 200 species exist worldwide.
Carnivorous Plant Diets
The predominant diet of carnivorous plants is insects. Depending on the method of entrapment, carnivorous plants will digest insects in various stages of development. Some thrive on the larvae of mosquitoes, while others rely on trapping flying insects. Some species of bladderworts eat microscopic organisms, such as soil-borne protozoa and paramecium. A few large species of pitcher plants eat small amphibians, birds and mammals that fall into the bottom.
Method of Digestion
Once their prey is trapped, carnivorous plants secret digestive enzymes. These enzymes break down proteins of their prey. Once the prey has decomposed the carnivorous plant absorbs the protein. The protein is converted directly into nitrogen for the plants to use in photosynthesis. Venus fly traps take between five and 10 days to digest their prey. Once they have digested and absorbed nutrients from their prey, their leaves open. Wind and rain remove the undigested portions of the exoskeleton.
Pitcher plants do not expel remnants of their prey; rather, they decompose slowly over time in the base of the plant. Sundew carnivorous plants digest their entire prey. Any part of the insect that touches the sundew is covered in digestive enzymes. Bladderworts have trigger hairs located around their trap door; when an insect lands, the door opens inward and sucks the prey in whole. Bladderwort digestion takes approximately 15 minutes.
Unique Predatory Flowers
Carrion flowers emit a foul odor that attracts flies and other flying insects that enjoy decaying remains. The female carrion flowers entrap the insects temporarily, unlike carnivorous plants, coating them with pollen. Once the male flowers have matured, the insects are released. This ensures cross-pollination and survival of the various species of plants.