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Carnivorous Plants: David Attenborough, Darwin, and the Venus Flytrap

July 8, 2010

“It is not the strongest of the species that survives, nor the most intelligent, but the one most responsive to change” – Charles Darwin

I, like most people, can listen to David Attenborough discuss plants and wildlife all day long. His Planet Earth series is just mesmerizing and stands as the most expensive nature documentary series even commissioned by the BBC. Also, one that takes great prominence in my home collection.

A close second in my classification of wonderful nature documentaries narrated and driven by David Attenborough is The Private Life of Plants, a BBC nature documentary from 1995. It explores plants as social organisms, strongly reactive and interactive with their surrounding habitat. It also touches one of the most interesting plant types anywhere: the Venus Flytrap.

The Venus Flytrap, aka Dionaea muscipula, is an absolute marvel of science, one that Darwin was mesmerized by. He referred to it as “one of the most wonderful plants in the world”, one supremely adaptable and aggressive. It is a carnivorous plant that evolved from conventional relatives with sticky leaves. Over time, it evolved to add elaborate weapons such as trigger hairs and “teeth” to trap prey. As for the name, I will leave that explanation to The International Carnivorous Plant Society (quite an amusing, informative read).

It ensnares and consumes flies, insects, and even small frogs. But it does so intelligently and socially. Basically, the Venus Flytrap has to conserve energy whenever possible. Possible prey approach the plant and trigger the trip by crossing a series of tiny hairs  on the plants surface. Crossing a single hair will not trigger the trap, however; two hairs must be crossed in a span of 20 seconds of each other to trigger the trap. Otherwise, the plant would be snapping shut all day long.

Once the trap shuts (and it shuts fast, at less than 0.3 seconds on average), it is a matter of urgency and most of that is predicated by the prey. If the prey struggles, it will continue to stimulate the trapping mechanisms and this will shut the trap tighter. Enzymes are produced which help digest the prey and all of this is sped by the struggle. A bleak prospect for the prey, more often than not a fly.

This snapping of the trap is referred to in scientific circles (at least the chemical reaction that stimulates this snapping) as the action potential and all of it is predicated on calcium deposits in the plant itself. It is not completely understood how all of this works, but there is osmosis involved as certain cells collapse and certain cells elongate and swell. Either way, it spells trouble for the fly.

The Venus Flytrap as rendered in Curtis's Botanical Magazine.

Want to learn more? See some of the following articles:

Affolter, J.M. & Olivo, R. (1975). Action potential in Venus’s-Flytraps: Long-term observations following the capture of prey. American Midland Naturalist, 93 (2): pp. 443-445. Retrieved from http://www.jstor.org/stable/2424177.

Jurgens, A. (2009). Do Carnivorous Plants Use Volatiles for Attracting Prey Insects? Functional Ecology, 23 (5): pp. 875-887. Retrieved from http://www.jstor.org/stable/40407697

Stuhlman, O. & Darden, E. (1950). The Action Potentials Obtained from Venus’s-Flytrap. Science, 111 (2888): pp. 491-492. Retrieved from http://www.jstor.org/stable/1676397

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