Tuesday, December 11, 2007

Of carnivorous pitchers and viscoelastic deaths

"A Viscoelastic Deadly Fluid in Carnivorous Pitcher Plants"
Its not everyday that a scientific paper with a title like this gets published. But it did, recently on PLoS one, the free access online journal that publishes papers from all disciplines. So, what did Laurence Gaume (biologist) and Yoel Forterre (physicist), the French authors have to say?
That carnivorous pitcher plants can get pretty sticky when it comes to getting their one course meal. Okay that doesn't sound too impressive huh? Take this..
All this time we spent in school reading about pitcher plants (genus Nepenthes) capturing insects by their slippery surfaces and the enzymes inside that digest the insect slowly... well thats not all. As it turns out this digestive enzyme in some species (Nepenthes rafflesiana pictured above being the star of the show here) has viscoelastic properties.
Apparently, thats the physicist and his fluid dynamics jargon speaking here.
In plain speak, the fluid has both viscous and elastic properties that ensure that once the unfortunate bug gets anywhere in contact with the fluid its in a real sticky mess. The viscoelastic filaments in this fluid act like a quicksand, coating the insect and making it immobile the more it struggles. Meanwhile it gets digested. What a way to die!
Oh yeah, thats not all. This miracle fluid works perfectly well even after 90 percent dilution with water. Which figures, because these tropical plants see a lot of rain and if a little bit of water ruined your whole prey capture mechanism, then grandpa Natural Selection would have kicked you out long back.
Messieurs Gaume and Forterre apparently had a ball doing this study using insect bioassays (read killed different insects with the same stuff to see if they die the same), high speed photography and rheological analysis (thats the physics geek there again!).

The Indian pitcher plant Nepenthes khasiana (left)

Public Library of Science journals
Carnivorous plants on Wikipedia

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