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Tag: pitcher plants

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    A Pitcher Plant’s Rain-Triggered Trap

    Pitcher plants all use slippery rims and sticky digestive juices to capture and trap their insect prey. But two species of pitcher plant independently evolved an extra trap: a rain-activated springboard lid. Both the Seychelles pitcher plant and the slender pitcher plant — separated geographically by 6000 kilometers — have a springy, near-horizontal “lid” that sticks out over their pitcher. The underside of the surface is slippery, though less so than the pitcher’s lip and walls. Unsuspecting ants crawl under the lid, confident that they can keep their footing, and then — bang — a rain drop hits the springboard. That impact catapults the insect directly into the drink. There’s no escaping now.

    How did two widely separated, independently evolving plants both settle on this technique? Scientists think it was random chance. Pitcher plants are highly variable in their pitcher size, shape, and features. The scientists suggest that by trying lots of random combinations, these two species hit upon a particular arrangement that works really well for them. (Video and image credit: Science)

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  • Rain-Driven Prey Capture

    Rain-Driven Prey Capture

    Pitcher plants often entice their insect victims with sweet nectar before trapping them in inescapable viscoelastic goo. But some species go even further. Nepenthes gracilis, a species native to Southeast Asia uses its leafy springboard to lure its prey. Once an ant crawls to the underside of the leaf, a falling rain drop will spell its doom. When drops hit the leaf, it deflects down and jerks up, thanks to its shape and stiffness. The motion catapults insects into the pitcher, where digestive fluids await. While we’ve seen some fast-moving plants before, this is a rare example of a plant with an externally-driven speed mechanism. With it, the pitcher plant doesn’t have to wait or expend any metabolic effort to reset for the next insect. (Image credit: GFC Collection/Alamy; research credit: A. Lenz and U. Bauer; via New Scientist)

  • Sliding Down a Pitcher Plant

    Sliding Down a Pitcher Plant

    Carnivorous pitcher plants supplement their nutrient-poor environments by capturing and consuming insects. The viscoelastic fluid inside them helps trap prey, but fluid dynamics plays a role elsewhere on the plant as well. The inner and outer surfaces of the pitcher are covered in macroscopic and microscopic grooves, seen above, oriented toward the interior of the plant. 

    Researchers found that these grooves trap droplets on the slippery plant through capillary action. Once adhered, the droplet cannot easily move across the grooves, but it can slip along them, carrying the droplet and any insect stuck to it, into the plant. By replicating pitcher-plant-inspired grooves on manmade surfaces, researchers found they were able to better control droplet motion on slippery, lubricant-infused surfaces than in previous work. (Image and research credit: F. Box et al.; via Royal Society; submitted by Kam-Yung Soh)

  • Pitcher Plant Fluid Dynamics

    Pitcher Plant Fluid Dynamics

    Carnivorous pitcher plants owe much of their efficacy to the viscoelasticity of their digestive fluid. A viscoelastic fluid’s resistance to deformation has two components: the usual viscous component that resists shearing and an elastic component, often derived from the presence of polymers, that resists stretching – kind of like a liquid rubber band. It’s the latter effect that’s important when it comes to the pitcher plant trapping insects. When a fly or ant falls into the liquid within the plant, it will flail and try to swim, thereby straining the fluid. In part © of the image above, you can see how long fluid filaments stretch as the fly moves; this is because the digestive fluid’s extensional viscosity, the elastic component, is 10,000 times larger than its shear viscosity, the usual viscous component, for motions like the fly’s. This viscoelastic fluid is so effective at trapping insects that, as seen in part (b) above, it has to be diluted by more than 95% before insects can escape it! (Image credit: L. Gaume and Y. Forterre)