email a friend iconprinter friendly iconCarnivorous Plants
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Today biologists using 21st-century tools to study cells and DNA are beginning to understand how these plants hunt, eat, and digest—and how these bizarre adaptations arose in the first place. After years of study, Alexander Vol­kov, a plant physiologist at Oakwood University in Alabama, believes he has figured out the Venus flytrap's secret. "This," Volkov declares, "is an electrical plant."

When an insect brushes against a hair on the leaf of a Venus flytrap, the bending triggers a tiny electric charge. The charge builds up inside the tissue of the leaf but is not enough to stimulate the snap, which keeps the Venus flytrap from reacting to false alarms like raindrops. A moving insect, however, is likely to brush a second hair, adding enough charge to trigger the leaf to close.

Volkov's experiments reveal that the charge travels down fluid-filled tunnels in a leaf, which opens up pores in cell membranes. Water surges from the cells on the inside of the leaf to those on the outside, causing the leaf to rapidly flip in shape from convex to concave, like a soft contact lens. As the leaves flip, they snap together, trapping an insect inside.

The bladderwort has an equally sophisticated way of setting its underwater trap. It pumps water out of tiny bladders, lowering the pressure inside. When a water flea or some other small creature swims past, it bends trigger hairs on the bladder, causing a flap to open. The low pressure sucks water in, carrying the animal along with it. In one five-hundredth of a second, the door swings shut again. The cells in the bladder then begin to pump water out again, creating a new vacuum.

Many other species of carnivorous plants act like living flypaper, snagging animals on sticky tentacles. Pitcher plants use yet another strategy, growing long tube-shaped leaves into which insects fall. Some of the largest have pitchers up to a foot deep and can consume a whole frog or even a rat unlucky enough to fall into them. Sophisticated chemistry helps make the pitcher a death trap. Nepenthes rafflesiana, a pitcher plant that grows in jungles on Borneo, produces nectar that both lures insects and forms a slick surface on which they can't get a grip. Insects that land on the rim of the pitcher hydroplane on the liquid and tumble in. The digestive fluid in which they fall has very different properties. Rather than being slippery, it's gooey. If a fly tries to lift its leg up into the air to escape, the fluid holds on tenaciously, like a rubber band.

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