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How a Venus Flytrap Snaps
Chris Gondek pastes in a few sentences: "A team of scientists led by a Harvard mathematician say they have solved one of the plant world's most intriguing mysteries: how the Venus flytrap snaps shut. Using a high-speed video camera and computer modelling, the team found that the flytrap employs an ingenious trick to slowly build up elastic pressure in its leaves, like the stretching of a rubber band, and then snap at the slightest provocation."
Pressure builds up in the cells, electrical impulses, etc. old stuff...
I learned this stuff in advanced ecology in college. One of the grad students even showed us the impulses on a computer. A Math grad student used this in a paper about the catastrophy point.
What exactly is new with this experiment? The article doesn't go into details.
94% of Repubs and 21% of Dems voted to renew the Patriot Act
So I read the article, rather intrigued. I wondered if it was water pressure inside the leaves. I wasn't so keen on the "it's like a rubber band..." theory, mainly because I couldn't figure out what forces pulled the "rubber band" back in order for it be right at the snapping point. Just what builds up the kinetic energy inside the plant?
After reading the whole article, they say this: "The exact mechanism the flytrap uses to change the pressures within the leaf remains unknown, Mahadevan and other scientists said." So it's still all theories and guesses, yah?
"He uses statistics as a drunken man uses lampposts...for support rather than illumination." - Andrew Lang
It's been my experience that a Venus Flytrap will snap when he's been around Les Nessman for too long.
I used to imagine this was a plant with some way of mounting stimulus-response behavior akin to animals so I, complete biology nincompoop that I am, was expecting news of the discovery of an alternative to nerve tissue or some such thing. Now I hear its mostly a mechanical trap. I hate having to constantly re-learn that nature is more clever than I am!
SLASHDOT: news for people who can't concentrate on work or have no life at all and got tired of yelling back at the TV.
I had a hard enough time in college with the teachers barely speaking engrish. This guys name is Lakshminarayanan Mahadevan.
Think his students call him Doc L? Mr. M?
Seriously, though, how many people on /. are gonna get a WKRP reference?
Danke tres mucho, tovarishch.
The rapid closure of the Venus flytrap (Dionaea muscipula) leaf in about 100 ms is one of the fastest movements in the plant kingdom. This led Darwin to describe the plant as "one of the most wonderful in the world". The trap closure is initiated by the mechanical stimulation of trigger hairs. Previous studies have focused on the biochemical response of the trigger hairs to stimuli and quantified the propagation of action potentials in the leaves. Here we complement these studies by considering the post-stimulation mechanical aspects of Venus flytrap closure. Using high-speed video imaging, non-invasive microscopy techniques and a simple theoretical model, we show that the fast closure of the trap results from a snap-buckling instability, the onset of which is controlled actively by the plant. Our study identifies an ingenious solution to scaling up movements in non-muscular engines and provides a general framework for understanding nastic motion in plants.
Plants are not known for their ability to move quickly. Nevertheless, rapid plant movements are involved in essential functions such as seed and pollen dispersal (exploding fruits in Impatiens, squirting cucumber and trigger plants), defence (sensitive mimosa) and nutrition (Venus flytrap, Aldrovanda vesiculosa, bladderwort). Of these spectacular examples that have long fascinated scientists, the leaves of the Venus flytrap (Fig. 1a), which snap together in a fraction of second to capture insects, have long been a paradigm for study; however, the mechanism by which this engine works remains poorly understood. The most frequently proposed explanations are an irreversible, acid-induced wall loosening, and a rapid loss of turgor pressure in 'motor cells'. However, the validity of both mechanisms has recently been questioned on the grounds that these cellular mechanisms alone cannot explain the rapidity of closure of the entire leaf on a macroscopic scale; this has led to the suggestion that elastic deformations might be important.
Any mechanistic explanation requires an understanding of the geometry of snapping. Therefore, we first quantified the change in leaf geometry during closure by painting sub-millimetric ultraviolet-fluorescent dots on the external face of the leaves and filmed closure under ultraviolet light, using high speed video at 400 frames per second (Fig. 1b, see Supplementary Methods for a movie). Using a pair of mirrors to record stereo images, we reconstructed the leaf geometry and the change therein using triangulation (Fig. 1b, c; see Methods). As Darwin had already noted, the leaf is curved outward (convex) in the open state and curved inward (concave) in the closed state (Fig. 1a). The leaf shape can be naturally characterized in terms of its spatially averaged mean curvature (kappa_m) and its spatially averaged gaussian curvature (kappa_g), both of which are invariant under rigid body motions and are thus indicators of shape. In Fig. 1d we plot kappa_m as a function of time and observe that the snapping motion is characterized by three phases: a slow initial phase (20% of total displacement in 1/3 s), a rapid intermediate phase (60% of total displacement in 1/10 s) and finally a second slow phase (20% of total displacement in 1/3 s). The existence of the three phases is consistently observed, but the quantitative values may vary. Most of the leaf displacement occurs in the intermediate phase, during which the leaf geometry changes from convex to concave. Figure 1e shows kappa_g as a function of time. We see that kappa_g is not constant, and also that kappag changes slowly and then rapidly as it passes through a minimum. As changes in kappag correspond to stretching the mid-plane of the leaf, these observations imply that closure is characterized by the slow storage of elastic energy followed by its rapid release.
To understand the origin of these curvature changes, we measured local strains by recording the position of fiducial markers over t
The same theme of building up tension or pressure behind a latch or spring (though not necessarily the exact same implementation as in the flytrap) is at work in the tongues of some frogs and lizards, in the legs of crickets and grasshoppers, and in click beetle flipping, to name a few.
"... curiosity about the everyday world" described as "quaint"; actually, "sad" is wrong... "scared" is more like it! Curiosity and the tendancy to think for oneself are, I believe, closely related. Those who would dismiss making the effort to find the interesting behind the common as "quaint* " are, in a fundamental way, dead.
*Note that the artical itself seems to be written from the viewpoint of one with a healthy curiosity and is NOT perniciously dismissive!
... clicky "oilcan" buttons like you get on the better class of calculator.