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Plants in our world evolved various kinds of defenses, like poison, urticating hairs, thorns etc.

What i dont see is plants that defend themselves by means of explosions.

The explosion by itself can stun or scare a herbivore and dennounce its position for possible predators, while on later stage of evolution, shrapnel launching plant might use explosions to launch small thorn-like structures towards predators.

How can a plant produce controlled explosions biochemically ? How can it prevent the explosions and shrapnel from damaging its own self ?

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    $\begingroup$ It seems to me like explosions would be more useful for a plant in spreading its seeds than in defending itself. But in either case, I think the reason no plants do it in real life are the energy costs. $\endgroup$ – sumelic Apr 23 '15 at 1:07
  • $\begingroup$ There are plants that explode mechanically (as if using springs of sorts) to disperse their spores, but i want true explosions, chemical explosions, used for defense. $\endgroup$ – Jorge Aldo Apr 23 '15 at 1:09
  • $\begingroup$ Reminds me of creeper in Minecraft $\endgroup$ – user6760 Apr 23 '15 at 2:53
  • $\begingroup$ @user6760 Minecraft creepers are actually quite likely to be plants youtube.com/… $\endgroup$ – Mike.C.Ford Apr 23 '15 at 9:33
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Explosions are an energy-inefficient form of defence against things that might want to eat you. You want to conserve all your hard word by warding-off animals. It's wasteful to spend time and effort into something that is going to go bang, once, when you could invest it in more permanent deterrents.

What is more plausible is explosions for reproduction. Specifically, launching seeds or pollen into the air. A better justification might be into the fur of animals eating the plant's fruit, so that said animal can do cross-pollination for you.

Bees do this with pollen today, and there are many species of plant that have thorny seeds that latch onto fur. In the case of bindii, painfully into the bottom of your foot when you walk across them.

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Plants already use mechanical explosions to launch their seeds. They are certainly capable of generating all of the chemicals needed for a chemical explosive - but really the evolutionary cost of doing so is very high.

An explosion is not just going to scare away predators, but is also going to destroy or damage the plant in the process.

I suppose it is possible that it could evolve out of a seed dispersal process, if chemical agents start being added to throw the seed further and further then eventually the plant will start accelerating the seeds to higher and higher speeds.

An evolutionary adaption could then cause it to deliberately fire the seeds at passing animals. If the seed kills the animal then it is lying in a bed of ready fertilizer. If not then it will be carried by the animal.

As a bonus scavengers may be drawn to the body, and they can then act as further seed carriers.

And now you've evolved a plant that actually shoots seeds like bullets at things!

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  • $\begingroup$ The dynamite tree: en.wikipedia.org/wiki/… $\endgroup$ – user3106 Apr 23 '15 at 10:02
  • $\begingroup$ Worth noting that this process is called "explosive dehiscence." $\endgroup$ – foobarbecue Apr 10 '16 at 17:48
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It is an inefficient method, but if it did happen, either chemicals or spines would be shot out of the plant. The spines would hurt and scare away predators. The most probable is an explosion of a pesticide made by the plant, killing insects if they eat the plant.

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Actually, I already designed an explosive plant, Pyroberries, for one of my prior settings. I considered the fact that evolution is unlikely, of course, but went with it anyways.

My solution to the high energy cost was not that they directly explode, but rather that the berries are filled with seeds and with pyrophoric liquid, and the berry design is such that when they are plucked, that leaves a gap open to the air, which causes rapid ignition. So no direct mechanical explosion process is required. Naturally the seeds themselves and most of plant are very hard and highly temperature resistant (but not the flesh of the fruit).

If some creature attempts to eat the berry, it sets fire to its tongue after a short delay and probably spits the stuff out, aiding in spreading the seed. If the creature is such that it is hardy enough to have a stomach literally full of napalm, the seeds survive anyway and come out as part of the waste products.

Also, for some reason, if so happens that nothing eats the berry for a whole season, the substance inside becomes inert, and it drops off the bush, rolling to a place where it can grow anyway.

As a nice bonus, the hard seeds make it so that these berries are effectively incendiary cluster grenades (just with dangerously short fuses). In fact, in that setting, they are the prime ingredient used in the manufacture of Thunderstones.

I'm aware this is not exactly what you probably had in mind; but its out there anyways.

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  • $\begingroup$ Eventually, other creatures would evolve to avoid the berry though, so it would no longer be spread via ingestion and egestion. $\endgroup$ – theonlygusti Apr 23 '15 at 18:48
  • $\begingroup$ Indeed, that's why there is still the clause that allows it to grow by dropping off and becoming inert. $\endgroup$ – eharper256 Apr 23 '15 at 18:52
  • $\begingroup$ Yeah, I'm just saying that eventually that would become it's only method of spreading, so its volatile nature would become redundant within less than a life-time, probably. Still, I've upvoted because it is such a cool idea, and your's seems to be the only answer which explains how volatile plants may be constructed :) $\endgroup$ – theonlygusti Apr 23 '15 at 19:36
  • $\begingroup$ Heh, thanks. I know my D&D players loved them... well except that time when they ~nearly~ accidently blew up an entire (fortunately uninhabited) island with them on lol. Though it wasn't really considered at the time when I made them, I like to think they have some appeal that keeps the animals challenging them or something (an attractive smell?). $\endgroup$ – eharper256 Apr 23 '15 at 22:46
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Two problems come to mind:

1) What's the evolutionary pathway? What does the plant gain from having an explosive too weak to do any good?

2) Explosives are by their very nature unstable. Remember, you have to judge a charge by the what it's like with the blasting cap in place. There's a reason the blasters store the caps separate from the explosives but the plant doesn't get to do so. How many defense charges are going to be wasted?

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