Traps and Trapdoors

Probably the best-known carnivorous plant is the Venus flytrap, which grows to a height of about 12 inches [30 cm]. Found in peat bogs in the Carolinas of North America, the Venus flytrap has shiny, brightly colored leaves that are edged with nectar-producing glands​—a temptation that is difficult for insects to resist! Therein lies the danger, for the Venus flytrap contains three trigger hairs in the middle of each leaf lobe. When an unwary creature touches them, the leaves close. Like the jaws of a steel trap, spines around the edge of the leaves interlock to prevent the prey from escaping.

If the trap closes on something that was blown into it by the wind​—a piece of dry twig, for example—​the plant will release it in a couple of days. But when the sensory organs on the leaf detect the presence of nitrogenous substances, enzymes are released to break down the captured insect’s body so that the plant can absorb the nutrients. This process takes from 10 to 35 days, depending on the size of the prey.

Interestingly, if just one trigger hair is disturbed, perhaps by a raindrop, the trap will not close. It is only when two or more trigger hairs are touched​—even after an interval of up to 20 seconds—​that the plant reacts. The speed at which the trap closes is dependent on temperature and sunlight. In certain conditions it closes at a speed of a thirtieth of a second.

[Picture on page 24, 25]

Venus flytrap

Leaf on left shows a trapped fly; leaf on right shows trigger hairs

[Credit Line]

Plants: Copyright Chris Heath, Kentish Town City Farm, London