Carnivorous Plant Adaptations

Carnivorous plants can trap and digest prey.

Carnivorous plants have evolved in ways that allow them to trap and digest prey. According to Barry Rice of the International Carnivorous Plant Society, there are three types of adaptations present in carnivorous plants. The first type of adaptations include specialized structures for capturing prey such as leaves that snap shut. Enhancements are adaptations that improve the plants' efficiency at capturing prey such as exuding an odor that attracts insects or a waxy surface that causes a landing insect to slip inside the trap. The last type of adaptations are modifications that permit the plant to absorb nutrients from the digested prey.

Pitfall Traps

Pitcher plants have long, deep cups that can trap insects.

Pitfall traps, also known as pitcher traps, are deep cups that have rain water or fluid in the bottom. Insects are drawn to the edge of the cup by a sweet scent or nectar, and some of them fall in. They drown in the liquid and are then digested. Some pitcher-type plants produce their own digestive enzymes. Others contain bacteria or other organisms that digest the prey for them. Once digested, the plant absorbs the nutrients. An example of a carnivorous plant with a pitfall trap is the pitcher plant. Besides nectar and scent, enhancements on pitcher plants that help draw prey may include colorful cups that resemble flowers.

Snap Traps

The Venus flytrap's leaves have evolved into traps.

The familiar Venus flytrap is an example of a carnivorous plant with a snap trap mechanism. The trap is made of two highly adapted leaves, often brightly colored to attract insects, with many sensitive hairs on the inside edges. The trap is triggered to snap closed when the hairs are disturbed by the touch of a landing insect. As the insect moves inside the closed trap, it continues to trigger the leaves to tighten even more. Eventually it seals shut, the prey suffocates and digestive enzymes are released.

Sticky Traps

Sundews catch their prey with a sticky substance.

Some carnivorous plants grow stalks or specialized leaves that exude a sticky substance that catches the insects that land upon it. They may draw their prey with odors or colorful structures that are not flowers. Once prey is caught, some plants produce digestive enzymes and others rely on a symbiotic relationship with another insect to digest it for them. Sundews capture their prey this way; they receive nutrition from the excrement of the insects who digest the prey for them.

Lobster Pot Traps

Plants that use this type of trap are found in both land and aquatic species. In the land plants, prey is drawn to a chamber where nectar is found; as it walks forward it reaches a point of no return. The plants have hairs that grow towards the interior and do not allow for backtracking. Some lobster pot traps lead to a pitfall trap where the insect drowns. Rice says that the draw in the aquatic Genlisea plants is unknown, but the mechanism is the same.

Suction Traps

Only the genus Utricularia uses a suction trap to capture prey. This plant lives in waterlogged soil or ponds. Part of the plant is above the water, but the pouches that are used to trap prey are underwater. These pouches, or bladders, can be as small as a pinhead to about 1/4 inch in diameter. Each pouch has a one-way door. Water pressure inside the pouch is less than outside; if prey bumps into the door, it will open easily. Once inside, the prey cannot push the door open again as suction holds it closed, and it is digested.

Absorbing Nutrients

This adaptation takes three forms. In some plants such as the suction trap Utricularia, there are specialized cells or structures which absorb nutrients from digested prey. In others the nutrients enter the plant cells directly, as in the pitcher plants. In the last type, the excrement of symbiotic insects is dropped on the leaves of the plant, and specialized gaps in the waxy cuticle covering the leaves allows nutrients to pass through.

References

• The International Carnivorous Plant Society: What is a Carnivorous Plant?
• The International Carnivorous Plant Society: Lobster Pot Traps

Resources

• The International Carnivorous Plant Society: Carnivorous Plant FAQ