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Is it possible to have plants that wouldn’t burn?

Having the plant getting damaged by fire is fine, but I want the plant not to burn at all. It does not need to survive, it just must not catch fire (for roughly an hour).

This is going to be a plant from another world, but I would like to know if this is possible with what we know of plant life on Earth. And if it is possible a little explanation as to how a plant could be fireproof would be greatly appreciated.

The temperature should be at least 1200 °C, but ideally I would like to have 2000 °C.

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    $\begingroup$ 2,000 C is very hot. Hot enough to melt iron, and turn most rocks into lava. Is that supposed to be general environment temperature in which the plants survive in the long term? No amount of water storage or other forest-fire protection are going to work against that. If the plant only has to resist such high temperatures very temporarily, then it can do so with defences that keep it cooler internally. $\endgroup$ – Neil Slater Oct 19 '15 at 16:14
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    $\begingroup$ Do you want something that doesn't melt too? When wood is heated in the absence of oxygen it turns into charcoal, basically all the impurities have lower melting points and come out first. the melting point of charcoal is about 3500 degrees Celsius. If the wood turns to charcoal are you satisfied that it didn't burn is what I'm getting at. $\endgroup$ – Captain Man Oct 19 '15 at 17:25
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    $\begingroup$ At 1200 - 2000 degrees I can turn metal into the shape of a plant. No biologically realistic organism is going to survive that. $\endgroup$ – James Oct 19 '15 at 18:53
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    $\begingroup$ Given the extreme temperatures you are looking at, well beyond the range of anything a reasonable person would call a plant, you may need to be precise in your definitions of "not burning." Does it just have to withstand being baked in a slightly oxidizing atmosphere for 1 hour at 2000C, or is the requirement "thou shalt not oxidize any atoms for 1 hour?" Can the plant create its own reducing atmosphere to prevent oxidizing(burning)? Can the plant allow parts of itself to burn while it constructs a non-burning region? Technicalities like that will matter. $\endgroup$ – Cort Ammon Oct 20 '15 at 2:16
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    $\begingroup$ There are a class of materials called aerogels, basically a lightweight foam that is mostly air, but makes an extremely good heat insulator. Perhaps this hypothetical plant evolved to include an aerogel in its cell structure. I'm sure there are other materials which could be useful to this plant.. $\endgroup$ – user2407038 Oct 20 '15 at 5:25

11 Answers 11

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To put something on fire, you need air (or another oxidizer), fuel (carbon inside the wood and leaves), and heat. Here are a few ideas how to delete one of them.

Reduce heat

A wood containing a lot of water does not burn well, as water reduces the heat while it evaporate. But even the most wet wood can burn if you set it one fire long enough, when all the water is gone.

Oxidizer

The plants could emit a gas that does not burn, replacing the oxygen around them by some fireproof gas (at lear near the ground, as they probably need oxygen to breathe somewhere).

Dinitrogen maybe ? I don't know what kind of gas would be the most likely. It should be heavy enough to stay near from the ground (I like the idea of a toxic gas-producing plant that does not burn).

Flames could not reach the plant. In a forest fire, the heat around could damage the plant but the wood itself could not be set on fire.

Fuel

Plants as we know them are carbon-based. You could imagine a plant made from something that doesn't burn but i'm not sure it will still be a plant, so let's keep carbon.

The wood from your plants could be wrapped in something that does not burn.

It could be something the plant itself produce, a kind of sap sweating from the wood, like the caoutchouc from the hevea tree (not the best example : the hevea does burn without problem, I checked on the net, there are many fires in hevea pantations, but your plant is an alien).

Or it could be something the plant does not produce, like an alien form of spider web. The plant could bring spiders or insects some food and the insects could build a kind of fireproof nest around the trunk.

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  • $\begingroup$ I also really dig the idea of the heavy-toxic-gas-producing plant that makes its own insulated region, it evokes some very cool images of what that would look like. It would take a pretty heavy blanket of that to stop an intense fire from penetrating it one way or another though, or getting dissipated by weather, so (I think) that would either require plenty of time to build up or the plants would have to have an intense metabolism and source of materials to maintain it. $\endgroup$ – thanby - reinstate Monica Oct 20 '15 at 11:53
  • $\begingroup$ Thing is, at the temperature the OP specified, you don't need the fire to reach the plant for it to burn. It is more than hot enough to autoignite. At this temperature, even most metals would melt away. So a protective coating of anything won't help for long, either. $\endgroup$ – Shane Oct 20 '15 at 13:41
  • $\begingroup$ I answered before the temperature edit, but you're right. However, fuel, heat and oxidizer are still needed to have flames and the question was to get plants that can't burn (but could be damaged by fire, they might change into coal if it's hot enough, without a single flame ? I'm far from sure). $\endgroup$ – Tyrabel Oct 20 '15 at 16:34
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Redwoods are fairly fireproof while alive. The biggest issue to keep from burning is heat displacement. So The red woods have a LOT of water stored in their bark as well as having a think bark of 'dead' cells. it can dissipate the heat by letting the water absorb much of it and evaporate away, leaving the trunk much cooler.

Being very large also helps dissipate the heat over a much larger volume. It takes a lot longer to heat a gallon of water than a pint.

I believe Aspen are also a natural fire break because they also resist fire, I think once again it is primarily due to volume of water vs. material to burn.

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    $\begingroup$ @Jimmery Nothing is impossible to burn. You can even burn pure Iron. All you can do is make it harder to burn, mostly by redirecting heat. So you would need to qualify how much heat it needs to resist. $\endgroup$ – bowlturner Oct 19 '15 at 15:42
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    $\begingroup$ you are right! i was being an idiot sorry! :) also, black smithing is a really awesome job/hobby - kudos! $\endgroup$ – Jimmery Oct 19 '15 at 16:12
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    $\begingroup$ @Jimmery not a problem, none of us knows everything, it's the willingness to learn that is important. And black smithing is my hobby. ;) $\endgroup$ – bowlturner Oct 19 '15 at 16:21
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    $\begingroup$ @Jimmery Some fire retardants are based on chemical action rather than physical action, so can be effective at low concentrations. Things like Halon an polybrominated diphenyl ethers have brominated compounds which will react with actively combusting materials and quench the chain reaction. $\endgroup$ – R.M. Oct 19 '15 at 16:38
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    $\begingroup$ @bowlturner: So you think anything burns. I can get you some fluorite crystals that will not burn if you want them badly enough. $\endgroup$ – Joshua Oct 20 '15 at 1:31
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Is it possible to have plants that wouldn't burn?

No.

In order for something to be alive, it needs to have a source of energy that it can use to power its internal functions, such as growth. This energy needs to be stored. A living thing releases this energy in what can be thought of as a very slow, very controlled burn.

It is this energy storage that means it is impossible for any living thing to be fireproof — heat up the energy storage enough and it will start releasing its energy. In the absence of oxygen the temperature at which it will burn is higher and not as much energy will be released when it burns, but it will still burn.

So how do you make a plant fire resistant? The plant needs a way to shield its energy stores from excess heat. The other answers have mentioned ways that a plant can protect itself to a certain degree.

Would a plant be able to protect itself from temperatures of 1200 degrees Celsius? No. 1200 C is the higher end for lava when it emerges. Here's a video of what happens when something organic is thrown onto lava — it explodes. 1200 degrees is past the point at which energy stores would spontaneous combust, oxygen or no.

The best way to survive that high of a temperature is to avoid it altogether. Animals can simply walk away (lava usually isn't that fast), but plants don't have that luxury. The quickest escape route for them is down. Basically, you have a plant with a large energy store (something like a bulb) deep underground. The part of the plant above ground will burn and die, but the plant will be able to regrow from its underground bulb after the lava has cooled.

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Unless these plants have some kind of magnetic shielding around them, they can't exist. 2000C is a full 600C above the firing temperatures of typical ceramics. (Cone 13 (1400C)is the highest temperatures found in conventional kilns. High-fired Superduty kiln brick only goes up 1600 or 1700C.)

Kiln Peep Hole

According to the Engineer's Toolbox, only a handful of metals have melting points above 2000C. They are:

  • Tungsten 3400
  • Rhenium 3186
  • Osmium 3025
  • Tantalum 2980
  • Molybdenum 2620
  • Ruthenium 2482
  • Niobium (Columbium) 2470
  • Iridium 2450

None of these materials are conducive to life using any kind of chemistry we know of. Organic materials are burned off for sure by 300C.

So if not metals or ceramics, what would work?

A magnetically shielded plant might be able to survive those temperatures. (If magnetic bottles are good enough to shape the plasma of torchships, then it out to do just fine against 2000C.) Since fire is a plamsa and reacts to electrical/magnetic fields, the plant could form a magnetic shield around itself to prevent burning up in such hellish temperatures.

Flame in an electric field

The problem will be in powering such a magnetic field and ensuring sufficient field strength over a sufficient duration to survive the required temperatures. A battery or capacitor would only last for so long.

A related idea is the Tesla Tree of Hyperion though there's no description of how these trees are constructed.

Tesla Tree

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    $\begingroup$ Physics says you only need energy to create a magnetic field, not to sustain it. Therefore it is not completely unreasonable that a tree slowly increases its field over years. But then again physics also says carrying requires no work which doesn't really work out in practice. $\endgroup$ – nwp Oct 21 '15 at 11:54
  • $\begingroup$ @nwp maintaining an steep heat gradient requires work. Thermodynamics indicates that the surrounding fire will try to heat up the plant. It takes energy to counteract that inflow of heat from highly energetic particles. $\endgroup$ – Green Oct 21 '15 at 12:00
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I was originally making this a comment but the idea evolved a little bit. So far everyone's suggestions have been for ways that the plant could suvive the fire, but you specifically state that it doesn't have to survive, just just can't burn. I'd like to put forth a suggestion that can meet the specific "die but not burn" criteria.

As some have mentioned there are a handful of naturally occurring materials which do not burn easily. Technically anything can burn given enough heat/oxygen, but since you've got a temperature threshold set we'll work with that. Quartz for example more-or-less fits within that threshold, as its melting point is over 1600 C.

Imagine a plant that uses seeded minerals in the dirt or deposited through rainfall to grow a casing of crystal. The crystal could server many purposes, like protection from certain elements in the atmosphere, protection from predators, aid in the plant's particular brand of photosynthesis, etc.

Chances are this plant would need some internal reinforcement to grow all this crystal and not fall over. It could have a wood-like exterior or even something resembling a skeleton. Or it could just have a thicker trunk section that tapers as it grows up, and short, stubby branches that don't need to support too much weight.

Now when a brush fire hits the area, the crystal would survive but the plant inside might be cooked by the temperature. If there are only small gaps in the crystal (remember it would probably need some gaps in order to breathe) you would end up with something that would screen the plant from actually igniting, sort of the reverse of the principles behind the Davy lamp which is something cool I just learned about the other day. If there's not a big enough gap in the crystal, not enough oxygen could pass through at one time in order to let the plant actually catch fire, but it would probably still be killed by the intense heat.

What you'd end up with after a fire is a field/forest of crystalline plant-shaped ghosts.

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    $\begingroup$ Or the organism could be dead to begin with. Petrified wood anyone? Or dead coral? That being said, the problem remains. I suppose those would still catch fire if the heat was high enough. $\endgroup$ – Stephan Branczyk Oct 20 '15 at 18:55
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The extreme temperatures you want to invoke in your world would be a serious problem for living creatures made out of any feasible substance. There are some compounds that do not melt at 2000 degrees Celsius, but they are not going to be suitable to construct a living thing by themselves.

What an alien plant needs to survive this onslaught is a way to keep the high temperatures away from its most vital parts.

I would suggest a plant evolved to cope with this extreme temperature would burn, but in a controlled and limited way. Around the thicker parts of its structure (main branches and roots), it would have a thick skin constructed so that when it was exposed to high enough temperatures, it created a thick insulating blister of carbonised foam (pure carbon has a very high melting/ablating point of ~3600C, although it would oxidise if the air contained oxygen). It would expand like some over-cooked carbonised popcorn, encapsulating the vital core of the plant in what would probably need to be a very thick insulating layer.

The plant would need to lose leaves, rootlets and other smaller structures that were not large enough to provide a thick enough insulating layer. They would just burn away. What would be left, hopefully, is a core of the plant that remained inside at a much lower temperature. Once the heat had gone, it would need to re-grow the lost parts from energy reserves kept aside for the occasion.

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If you want the plant to not burn at all, you must somehow suppress the fire from ever beginning due to the heat.

This can be done by a variety of techniques, but they all boil down to the fire pyramid:

enter image description here

In order to prevent fires, you must remove one of the edges from the fire pyramid. If you want the plant to not burn at all instead of merely surviving the fire, you must remove the Oxygen component, since the ambient temperature is already high, and the fuel already exists in the plant.

This can be done if the plants can produce large amounts of chlorofluorocarbons or other chemicals that displace oxygen and other oxidising gases, preventing the fire from starting due to the lack of oxidiser. This makes the plant similar to a natural Halon fire extinguisher.

Meanwhile, the requisite photosynthesis gas exchange can be performed using structures that extend above the protection of the fire extinguishing compounds. They are therefore vulnerable to fire, and have to be replaced after each fire cycle.

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The mature ponderosa pine (pinus ponderosa) is able to survive so-called "normal" fires. It does that by growing thick bark and by dropping lower branches while maturing. However less frequent more intense fires will jump into the crown and kill the tree.

Similarly fire resistant thick-barked trees are longleaf pine, slash pine, loblolly pine and giant sequoia.

Oddly the Australian eucalyptus manages better fire resistance than bark thickness would indicate. Possibly lower bark moisture content accounts for this.

References:
https://en.wikipedia.org/wiki/Fire_ecology#Plants
http://riel.cdu.edu.au/publications/register/riel1810
http://www.agf.gov.bc.ca/range/publications/documents/fire4.htm
http://www.nps.gov/fire/wildland-fire/learning-center/educator-resources/lesson-plans/fire-adaptation.cfm

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You've assumed the world is earthlike with similar pressures and air ratios. Can you redefine the world so that combustion is impossible - remove most/all the oxygen? Drop the pressure so that fire simply lacks the ability to start? I can't imagine a sea plant catching fire while under water.

Size may be another saving grace - if your plant is so big that an entire continent would need to be on fire before "the whole plant" is burning ? Consider strawberry runners where each node is a separate plant but they grow outwards.

Fire needs an oxidiser, a fuel, and a spark. The plant's form is the fuel, can your plant focus on removing one of the others? If the plant was large enough and stored a lot of water - could it function as an organic water main pipe and effectively extinguish fires by drawing water over long distances?

Finally, can your plant reject flame somehow - I believe wind would be bad if it contains oxygen, can the plant store argon or nitrogen or something else inert and non-flammable? This could be like a MIG welder releasing gas to keep the fire away.

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Your prerequisites are too hard for wood. At those temperatures over that time, any wood composed of organic materials will undergo pyrolysis and burn.

But since it is not necessary for the tree to survive, maybe what remains need not be wood?

Trees transport much of their water near the surface of the trunk with deeper layers largely "gunked up" and unable to be much other than structural support. Of course, structural support is vital so this is generally fine for most trees.

But we could assume (with usual note about ass-u-me fully applying), a tree that instead has symbiotic microbes capable of dissolving and consuming such "inert" wood. The released nutrients and space could then be used by the tree. Such tree would grow width very slowly since instead always growing new layers outside the previous ones, it would push new growth inwards where now dissolved and consumed wood was.

Now to the relevant part... We could further ass-u-me that some inorganic compounds would be insoluble, highly stable, and biologically useless to the tree. Such compounds would deposit as minerals in the core of the tree. Since deposition would happen at areas of low flow and flows are vertical, the deposition would be a continuous vertical structure. This would be favoured by evolution since it would provide the tree with longitudinal support.

The real issue is that while such minerals would, being chemically inert, perfectly realistically not burn, the high temperatures in the question will melt most minerals. Such melting would then cause the core to become a puddle with some sand in it, which is not adequate.

So let's ass-u-me another hypothetical system that conveniently transports minerals with lower melting points outside to provide the tree with bark that doesn't burn in normal fire and will give even beavers indigestion. Such tree would leave behind a core of hard stone in the shape and to some extent structure of the tree that created it.

Suitable minerals for the core might be quartz and corundum. Both silicon and aluminium are common in the soil and generally useless to organisms. The rock core would have lots of impurities from other minerals so I guess it would end up being kind of indistinct in color and appearance. While the minerals are hard I doubt such biologically deposited highly impure mess would be. Which might reduce brittleness.

Both quartz and corundum have melting points in the right range, so as long as the core is not too impure it might survive the heat for few hours with superficial damage. It certainly would not burn. It might even become harder. I doubt anyone would confuse it with wood, though, despite the shape and structure.

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To add another answer than "water doesn't burn", you could check out:

Make yourself as small as possible

If you have a lot of surface area, you have a lot of area to heat up through. If you make yourself small, the area the fire can touch will decrease, thus it'll be able to survive longer before burning up. Just imagine yourself curling up, you hide almost 50% of the surface! In case of the plant, only the outer layer will take the big punches, leaving the core of the plant (somewhat) intact.

There are plants which curl up when touched, or like the venus fly trap close up when there's a fly, so plants are capable of some movement. Just image a version where ir compacts/twirls up all together, as close to the ground as possible. Less surface area means less effect by the fire.

Shield yourself

There is a material called Aerogel, which is about 99% air. There is a lot of air trapped inside the material. Because of that, the stuff is an excelent insulator! You can barely feel the heat on the other side of the material. There are more of these materials available. There's a tv show (can't come of with the name) which makes a person touch one side of a sheet, and then a guy with a flamethrower goes mad on the other side. The result: His hand got a little warm.

The plants could have some sort of (chemical) reaction and create a foamlike substance which acts like the Aerogel does. The plants aren't in lab conditions, but any shielding will add time until the plant gets damaged too much. It could be that the plant can create more and more for a while, keeping the shielding 'fresh'.

Dig yourself in

This doesn't require a lot of creativity, but it does do the job. In case of extreme heat, dig in. Twirl into the ground so that your a few centimeters below the dirt. It'll still be hot, but you have an insulator now, again buying it some time.

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    $\begingroup$ Add intumescent materials to "shield yourself". These are materials which expand into insulating foams on heating. The chemical reaction which causes the expansion can also absorb heat (endothermic) thereby keeping whatever is inside cooler for longer. AFAIK there are no plants on Earth with intumescent bark, but I don't find it hard to imagine one. They'd need some time after a fire to shed the used protection and to grow a new coat. $\endgroup$ – nigel222 Oct 20 '15 at 16:10

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