Science North: Meat-eating plants 0
Did you know that there are plants, around the world that hunt and eat animals? This realization may conjure up images of the production Little Shop of Horrors, where the large meat-eating plant kept requesting the main character for more food. In reality, carnivorous plants are relatively small and hunt for insects and small invertebrates.
Carnivorous plants live in nutrient poor environments. Most species in Ontario can be found in wetlands. To obtain necessary nutrients, carnivorous plants have evolved a "hunting ability." These plants lure insects and other small invertebrates, trap them, and then digest their bodies to absorb nutrients .
The sundews (Drosera rotundifolia) are probably one of the most common species of carnivorous plants in Ontario. They have small leaves at their base and a 1.5-5 cm long vertical stalk with a bulbous red tip that is covered with hair-like extensions. These hair-like extensions are covered with glistening drops composed of sugars and a sticky substance. Insects are attracted to the drops, but once they land on the red tip they become stuck. The hair-like extensions wrap around the insect and the plant releases enzymes that digest the prey.
Pitcher plants (Sarracenia purpurea) are another common carnivorous plant. These plants are about 5-10 cm long, with a single nodding purple flower and a number of tubular leaves featuring bright red to purplish veins. These tubular leaves act as a pitfall trap to capture insects. There is liquid at the bottom of the tubular leaf that serves to drown and digest insects. To prevent the prey from climbing out of the trap once they are in, the leaves have evolved downward pointing hairs on the interior surface making it impossible for insects to escape. Insects are attracted to the smell of the plant, climb or land on the edge of the tubular leaf and fall into the bottom where they are digested.
The third carnivorous plant in Ontario is aquatic. Bladderworts (Utricularia vulgaris) live in marshes and ponds. They produce small yellow stalked flowers (about 5-7 cm long) that
emerge from the surface of the
water. The remainder of the plant floats in the water, and has thin stems with finely divided leaves. What makes this plant special is the small air-filled sacs (0.2-1.2 mm) or bladder attached to the stem. Each bladder has a small hair-like extension and a trap door at one end. Under normal conditions, the trap door is closed and the interior of the bladder is maintained under negative pressure. If a small animal such as an aquatic insect or a zooplankton brushes against the hair-like extension, this triggers the trap door to open and the animal gets sucked into the bladder. The trap door immediately closes behind the animal preventing it from leaving the bladder. This trapping process occurs in a matter of milliseconds, making it impossible for prey to escape. Once in the bladder, the prey will be digested and nutrients will be incorporated into the plant.
It's fascinating to see how evolution can shape the feeding habitats of organisms including these carnivorous plants. Next time that you are in a wetland, keep an eye out for these meat-eating plants.
Bruce Doran is a staff scientist at Science North. He welcomes all questions and comments and can usually be found on the third level of Science North. You can also reach him via Twitter: @BruceRDoran.