Carnivorous plant has a secret deep inside

BEN HIRSCHLER

Reuters

November 20, 2007 at 8:10 PM EST

LONDON — The carnivorous pitcher plants that feed on insects in the Asian tropics may not snap shut like Venus flytraps, but they are smarter than they look.

Rather than being passive pitfall traps, the tube-like pitchers of Nepenthes plants actually contain a clever slimy fluid -- similar to mucus -- that produces powerful filaments to snare prey, French researchers said on Wednesday.

The unusual qualities of the fluid could one day be used to develop new, less environmentally harmful pesticides, the experts believe.

Just how pitcher plants catch their prey has intrigued biologists since Charles Darwin's time. Until now, it was thought that gravity and the slippery tube surface were the key, with the fluid in the pitcher simply helping digestion.

But Laurence Gaume at the University of Montpellier and Yoel Forterre from the University of Marseille have discovered that the fluid actually has the perfect viscoelastic properties to snare flies and ants.

"The elastic nature of the fluid is responsible for the huge spring-back forces that act on moving insects," Dr. Forterre said.

"The only chance for insects to escape the fluid would be to move slowly. But once they've fallen in the pitchers, insects most often panic and exhibit quick movements. It is like swimming in jelly."

The effect is seen even when the fluid is diluted more than 90 per cent with water, as can happen during heavy rainfall in the jungles of Borneo, where many of the plants grow.

The researchers have yet to identify the molecules responsible for the elastic properties of the fluid, which appears to be unique in the plant kingdom. But they believe the ingredient could help produce better pesticides in future.

Viscoelastic fluids or polymers are often added to pesticides and herbicides to prevent sprayed droplets from bouncing off plants, so limiting soil pollution.

The fluid from Nepenthes could provide new polymers that are both highly effective and environmentally friendly.