December 19, 2012
Pitcher Plant Creates ‘Waterslide Of Death’ For Its Prey
Watch the video "Ants Aquaplaning On A Pitcher Plant"
Brett Smith for redOrbit.com - Your Universe OnlineResearchers from the University of Cambridge have observed for the first time how a Venezuelan pitcher plant uses moisture on its tiny hairs to create a ℠waterslide of death´ that sends unsuspecting ants further down into the plant, where they are eventually digested.
According to a new report in the Proceedings of the Royal Society B, the plant´s tiny hairs, known as trichomes, were previously thought to act only as a water repellant. However, the Cambridge researchers who conducted the study — along with collaborators from the University of WÃ¼rzburg in Germany — also noticed that the hairs were able to retain water. This observation inspired them to explore whether this feature might help the plants to entrap insects.
In the study, the ecologists used force measurements and several experiments to show how a wetting of the plant hair affected the ability of the ants' adhesive pads to anchor to the plant. The team observed that wet plant hairs resulted in ℠aquaplaning´ that caused the ants to glide across the plant´s surface and drop into the its pitcher.
"When the hairs of the plant are wet, the ants' adhesive pads essentially aquaplane on the surface, making the insects lose grip and slip into the bowl of the pitcher,” said lead author Ulrike Bauer, from the University of Cambridge. “This is the first time that we have observed hairs being used by plants in this way, as they are typically used to make leaves water repellent."
The aquaplaning mechanism caused by wet hairs increased the plant´s ant-capture rate to 88 percent — up from 29 percent when the hairs were dry. The researchers also noted that while the wet trichomes were effective against the insect´s adhesive pads, the inward-facing direction of the hairs was also effective against the insects´ claws.
In times of low moisture, the trichomes were also seen drawing up moisture from the bowl of the pitcher through a wicking action, thus allowing the plant to continue taking advantage of the aquaplaning effect even when water is scarce.
“This very neat adaptation might help the plants to maximize their nutrient acquisition,” Bauer said.
The Venezuelan pitcher plant, also known as Heliamphora nutans, is the first such plant to be described and is the best known species. It thrives in the Guyana Highlands of Southern Venezuela, living between 6,500 and 8,800 feet above sea level.
The area´s relatively sparse population has resulted in almost no impact on the local tropical rainforests and highlands. The majority of people living in the area inhabit a narrow strip of land near the Atlantic coast, leaving over 80 percent of the country's interior tropical forests untouched.
The pitchers can grow from a subterranean rhizome to reach 7 inches tall and about 3 inches wide. While considered a carnivorous plant, the Venezuelan pitcher plant does not make its own digestive enzymes. Instead, they rely on the enzymes of symbiotic bacteria to metabolize their prey.
The plant was was originally discovered in 1839 on Mount Roraima by two German botanists. In 1881, English ecologist David Burke found specimens and introduced them to his native country.