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We have Venus flytraps which move by closing their 'mouth' to trap prey. There are currently few identified plants with a 'quick' reflex like this. Blooms of course open and close through the course of a day and evening but that is pretty slow.

We've all seen things like 'The Wamping Willow' in Harry Potter and the man-eater in Little shop of Horrors or the Crawling vines in Jumanji.

I was wondering what kind of movement and reaction time would a plant be able to accomplish (while still remaining mostly a plant) whether to trap, entice or ward off animals. Could a tree have say vines on the ground that could be triggered by walking and they would just roll up like a carpet fast enough to trap an animal kill it like a boa constrictor (or add poison spines)?

EDT: "While still remaining mostly a plant", I mean I'd like to keep it as close to known plant biology as possible, but since no known plant can do these things, then some fiddling will have to be done.

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  • $\begingroup$ The problem with this question is: How much you can diverge from being a plant and still be a plant and not something else? $\endgroup$ – Monty Wild Feb 25 '15 at 0:39
  • $\begingroup$ A plant needn't be fast to trap an animal, if it can give the animal a reason to stay for several minutes, it could slowly close around it until it's too late for the animal to escape even if it notices. $\endgroup$ – Johnny Feb 25 '15 at 1:34
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    $\begingroup$ I'm tempted to create a joke account as a sentient plant, and respond to this question in a few years. $\endgroup$ – KSmarts May 7 '15 at 17:17
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The problem I always have with the fictional examples you gave is that those aren't actually plants any more. They're animals, with muscles, nervous systems, etc to be doing that.

That said, it seems quite reasonable to imagine a tree like you suggest. If a venus fly trap can move at that kind of speed, why not other plants? We can't really have muscles and call them plants, but we can have hydralic/pressure driven systems. So: Imagine a "vine" of some highly stretchy plant matter. There's a lot of spring energy in it, and the natural configuration is all coiled up. The plant then fills this up with liquid, which makes it straighten out and hang down. When an organism disturbs it, they knock off some weak covering over holes in the vine. The fluid escapes and the vine coils up again. (Bonus option - the fluid is also some kind of nerve agent). Not at all sure if it would actually work, but it's something.

The bigger problem you've got here is why a plant would do such a thing. It's not going to work as defence against being eaten (most traps are going to be single use, and there's going to be aways around the traps, poision or thorns work better for cheaper). If you're struggling for minerals etc for growth, how do you get to be a big tree full of nerve agents in the first place. Maybe it's part of a symbiotic relationship like the Bullhorn Acacia. It captures organisms to then be devoured by it's residents, who in turn protect it from anything that tries to eat the plant.

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  • $\begingroup$ Yes, I know my movie examples were more animal than plant, that's why I mentioned I'd like them to be much closer to plant, and my example. +1! $\endgroup$ – bowlturner Feb 25 '15 at 14:08
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You've various things like sensitive plants that react quite quickly.

This one, for example: https://www.youtube.com/watch?v=BLTcVNyOhUc

And if you watch a timelapse of a bramble growing: https://www.youtube.com/watch?v=aNjR4rVA8to

It'll wrap around something and 'strangle' it.

But you don't have much strength in a plant - it can fold up, but not push anything out the way particularly.

However enter urtica diocia - the common nettle - it 'stings' via brittle hairs, rather than thorns. They're almost like glass, in that they snap off and deliver a poison. But they'll sting if you just brush against them.

http://www.bbc.co.uk/programmes/p00gj39c

And then, you look for something more toxic. Like this: http://en.wikipedia.org/wiki/Dendrocnide_moroides

So I'd envisage a combination of the 4. A bramble like 'tendril' that curls up around something when it's touched, brushing against it to sting. And 'prickles' it with neurotoxin filled nettle-like hairs.

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  • $\begingroup$ Wow, that Dendrocnide moroides sounds horrible.... $\endgroup$ – Brad Werth Oct 21 '15 at 4:47

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