What are carnivorous plants?
While most plants rely solely on sunlight, water, and soil for their nutrients, carnivorous plants are special, since they also consume other living things to survive. Carnivorous plants can be found all around the world, typically growing in environments without many nutrients in the soil. These cunning plants have adapted a variety of ways to trap, kill, and digest insects, birds, and even small mammals to supplement their diet.
What makes carnivorous plants special?
Carnivorous plant species have developed five main types of traps: snap, pitfall, flypaper, bladder, and lobster-pot. These traps can be classified as passive or active depending on whether or not the plants move to ensnare their meal. After catching their prey, carnivorous plants use enzymes or bacteria to digest and absorb nutrients like nitrogen and phosphorus.
Our conservatory is home to one of the most iconic carnivorous plants: the Venus flytrap. The ends of this plant’s leaves meet to form a snap trap that can quickly ensnare unsuspecting prey. When an insect lands on a flytrap’s leaves, it brushes against the hairs on its surface, thus triggering the trap to clamp shut. To prevent losing too much energy from repeatedly opening and closing, the flytraps only shut completely if two of their trigger hairs have been touched within a few seconds of each other. Venus flytraps grow in the bogs of North and South Carolina, where the soils lack the nitrogen and calcium they need to grow. These conditions have led Venus flytraps to prey upon insects for their nutrients instead.
Enticing their prey with sweet nectar, pitfall traps are a type of passive trap system. Inside their pitcher-like structure, pitfall trap plants secrete sweet nectar to attract insects. As their prey gets drawn closer to the nectar, they slip on the pitcher’s waxy lining and fall down inside them. Heliamphora, Sarracenia, and Nepenthes are all examples of pitfall trap plant genera growing here in the Conservatory. Many Nepenthes, also known as monkey cups, are remarkable for being epiphytes, meaning that they can grow on other plants instead of in soil.
By secreting a sweet, glue-like substance called mucilage, some carnivorous plants use flypaper traps to capture small insects. These mucilage droplets resemble nectar droplets which helps entice insects to land on them. The Conservatory is home to two types of flypaper trap plants: Drosera and Pinguicula. Drosera plants entrap prey in mucilage by wrapping their “tentacles” around them. Pinguicula plants have broader leaves with glands designed to release more mucilage once an insect is detected, thus encasing the unsuspecting prey in the sticky substance.
The bladderwort, or Utricularia plants growing at the Conservatory have traps that utilize osmosis to pump ions in and water out of the plant. This creates a vacuum seal to the trap’s entrance. When an insect brushes against hairs on the trap door, the vacuum seal is triggered and the prey is instantly sucked into the bladder trap. Insects unfortunate enough to be sucked into these traps are slowly digested inside the bladder as the plant prepares to inhale its next victim.
Finally, the Genlisea genus of plants have lobster-pot traps that are specially designed for their prey to cluelessly wander into. The chambers of these traps are covered with hairs that point upwards, making it difficult for the protozoa they feed on to ever escape them.
Fun facts
Nepenthes lowii is a species of pitcher plant that has a unique mutualistic relationship with the tropical tree shrews and rats in their habitat. The pitcher plants attract these rodents by secreting a sweet nectar. After having their fill of nectar, these animals poop inside the pitcher plants. The Nepenthes Iowii use this excrement as a source of nutrients, since the plants grow in soil that lacks the minerals they need to thrive. In the end, both the rodents and carnivorous plants benefit from this unique relationship.