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You may have heard of pyrophites : They are plants which have a strong relationship to fire, whether they are extremely resilient to it, blossoming with it or simply as a way for their seeds to sprout.

I am devising such a plant that has an aggressive way of expanding, burning their surroundings to ensure they will get light, and maybe even retrieve specific resources from the cinders. Kindikinda like Slash-and-burn agriculture, without the slash part. This plant would emit slow-falling spores or seeds, very hot to the touch, and which may be even in flames as it lands on the ground.

For that purpose, I would like to know if such seeds could exist? The seed can be any shape and material you can imagine, as well as the type of plant producing it (tree, bush, grass, mushroom...). However, I'd very like it to respect physics, and to be based on concepts close (though not necesarily the same) to real world biology and chemical equivalents. Still, I won't be sad if you don't bring up scientific documents and calculations to support your solution (unless it's extraordinary, of course).

To help you, below are specific goals I wish to reach.

  • The seed, at its landing, should make at least dry grass burn. Ideally, this should be doable on wet grass or other plants. Therefore, they should be also quite hot.
  • Keep a hot temperature at the touch if you catch it during its flight. At the very least warm, but I'd rather have something uncomfortable to keep in your bare hands or even dangerous to hold.
  • [Secondary] Produces itself (or through the plant) the heat that makes it feel hot.
  • Be able to fly/glide on its own to reach new places to grow and to avoid annoying its parent. So pretty far away, and high enough. There can be winds, and even a strong upwind coming from fire around the plant to give them a head start.
  • Be strongly resilient to a continuous, high-temperature during its lifetime. The seed must sprout one time or another :).
  • Small-sized OR very slow falling basketball-sized fruit ones : Being small gives the seeds many more uses, and it would be so nice to have raining fire seedflakes ^^. But, I also had the idea of making them bigger sized, burning jellyfish or floating chinese lamp-like fruits. Nothing really between the two, however.
  • [Secondary] The seed can start a flame on its own through a sun-independent mechanism. Some pyrophites are naturally prone in making fire through sunlight and inflammable oil production, but maybe this can be automated without the sun's help?
  • [Secondary] Be able to keep a flame during the travel. That is, find ways to have a flame persist, like a candle last longer than a match. The longer it can keep it, the better.

Note that I tagged some objectives with "[Secondary]" : If you can't reach that goal from a scientific approach, then simply waive it away telling that you haven't managed to make it (that's okay! I can understand ;)). Then continue on, supposing this goal is reached through magical or other unknown means or is simply isn't part of the solution. Still, the more goals you can complete and include at once, the better it is!

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  • $\begingroup$ My answer literally satisfies all of these. $\endgroup$ – Firestryke Dec 5 '20 at 0:42
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Bear with me here.

So your seed has an outer gel coating that is extremely flammable and will burn hot for a decent amount of time. Then an inner protective layer which separates the seed part of the seed from the flammable part.

These seeds are contained in a large-ish gas sac filled with flammable gas. And on the outside of those gas sacs, there are little bulges that contain two separate chemicals that, when pressure is applied, the separating barrier breaks causing them to mix, which results in a mini-explosion that ignites the gas sac, causing the whole thing to explode.

When it explodes, it launches those seeds into the air and ignites them so that their outer coating is on fire.

When the seeds land, the coating sticks whatever it lands on causing it to set on fire. The seed of course is non-flammable so it survives and when the fire burns out, it has all this wonderful ash fertilizer to grow in.

Now, how do these sacs get the pressure they need to activate the chemical reaction? Simple, there are multiple of these sacs, and the gas inside them is lighter than air so that they kinda float like a balloon. They are of course attached to the trunk of the plant so that they don't float away, but when an animal, insect, or just a light breeze comes along and either bumps against or causes the sacs to bump against each other, it activates the combustion mechanism and boom you have exploding gas sacs, sending flaming seeds all over the place.

Now as to the flameproofing of the plant itself, that's simple, the plant secretes a flameproof gel onto the outside of the plant making it fireproof.

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  • $\begingroup$ So... If I understand well, the seeds are contained in pressure-sensitive explosive pods, whose task is to send and ignite said seeds. Clever thinking. Just a question, what shape would need the inner seeds to be to optimize the burn time? I'm worried I'd need to add a very big layer of gel to last long enough to land. $\endgroup$ – Tortliena Dec 6 '20 at 3:24
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    $\begingroup$ @Tortliena something like petroleum jelly burns pretty hot and for a while. But shape-wise I would recommend having several pore-like indents in the seed to fit more gel in $\endgroup$ – Firestryke Dec 6 '20 at 14:52
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Many of these requirements should be achievable, although it may require some hand waving. Quite a few chemicals spontaneously combust when brought into contact with other chemicals. Many of the alkali metals combust on contact with water or oxygen, although both of those will likely be present everywhere in your plant, so this is not a good idea. Sulfuric acid produces flammable hydrogen when encountering metals and will produce heat when mixed with water. This could be used to start combustion when needed. All of these chemicals are able to be produced in living organisms and this is therefore probably an okay option. These could be stored separately in an outer casing around the central seed and could be mixed when needed. Sulfuric acid may degrade over time or entirely destroy the seed, so if anyone has any other suggestions then please tell me.

The inner seed would need to be fireproof and the outer shell would need to contain some flammable oils. The seed could also utilize a "hot air balloon" type of floating by using its heat to produce hot air, which is lighter than cold air. This would be more effective with a larger balloon size due to the square-cube law, although smaller seeds could augment their flight with wing-like structures.

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    $\begingroup$ Flaming when active, and corrosive when it isn't. Dangerous for anything that tries to prey on them! To increase resistance to the acid, I can see two solutions : Dilute the acid until you need it, moving the problem on how to reactivate the solution, or find an acid resistant material. It just needs to be something plants are known to be able to make... $\endgroup$ – Tortliena Dec 6 '20 at 4:01
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There are many such as you describe.

lodgepole pine cone

https://www.landscapesinmotion.ca/updates-1/2017/11/10/a-wildfire-story-severity

"Serotinous" seeds which require a fire trigger to open are common in parts of the world where fire is common. I am familiar with the lodgepole pine from the northern US.

https://www.nps.gov/articles/wildland-fire-lodgepole-pine.htm

The bark of lodgepoles is thin, which does not protect the trunks from scorching by fire. They die easily when a fire passes through. However, the serotinous cones give lodgepole pine a special advantage for spreading seeds for the next generation. These cones are closed tight with resin that melts during a fire and releases seeds that have been stored for years. These seeds germinate in conditions that favor the tree’s seedlings, where the forest floor is clear and plenty of sunlight shines through an open canopy.

The cones can open by catching fire, or just by getting hot. The one depicted here burned a little but will be fine and is getting ready to make a tree. I will testify that it is possible to burn these cones completely in a campfire, but if you get one lit by itself it will generally go out. There are other pine species that do this as well as unrelated species. https://en.wikipedia.org/wiki/Serotiny

Your only difficult ask is the slow fall. To be triggered by fire but not have the seed itself burn, these fruiting bodies and seed cases need to be reasonable robust, or wet, or both which means they will probably fall pretty fast and not drift around like dandelion fluff.

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Hay fires

I can't find the English name, but the principal behind hay fires could be a solution.

Hay fires start because bacteria will start some awesome biological processes during their hay consumption. This requires a highly moist environment within the hay. The consumption process releases heat, which in turn quickens the bacteria. At around 55°C (131f) flamable gasses start forming, heating the hay further. This has several stages, but the most important thing is that when it heats up enough and gets oxygen, it'll combust.

This likely won't be directly applicable to seeds. However, it does show that with the right proteins and such you can make something hot and combust. The plant can do something similar with overpowered mitochondria or heat generating proteins together with a gas. It'll be hot to the touch and if you give the seed several phases you can potentially create the scenario you want.

Example how it could work: Seed grows on the plant. When the seed reaches maturity, the plant starts the process to release the seed.

The seed will start internal processes at a certain point, heating up.

The plant can react to a certain amount of heat, flinging the seed or severing it. Thermic reactions take a lot of energy, so you want the heating to only be done when at the best moment. Making the plant let go of the seed when it reaches a certain temperature makes this happen.

The seed will fall down, possibly moving on the wind if enough flight assistance is grown.

Seed will likely settle on time for when the heat is high enough for the next heat trigger, releasing the gas to the oxygen and will catch fire.

Problems

The seed likely needs to be rather large to have enough energy to heat up significantly, produce enough gas for the initial burning and fireproofing of the seed. This will impede easily floating on the wind, unless you decouple the firestarter and the seed (launching fire first, seeds after). Regardless, heating up just requires a ton of energy and will always be a problem for the size. Basketball sized seeds would help, allowing also multiple seeds to be held.

If you accept the plant to be (partially) burned, you can also just set fire to the surrounding area and let the seeds fly on the updrafts of the hot air.

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  • $\begingroup$ Yes, burning around the plant (through any reason) is allowed. With this fire relationship, having some resistance to it is vital if one seed fails and land too close to the plant. About "hay fires", I think it was the cause of one of "devil"'s event that happened in a village in history. Doesn't the gases need to be held in something? Otherwise it'll just dissipate, right? $\endgroup$ – Tortliena Dec 6 '20 at 3:32
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    $\begingroup$ @Tortliena hay fires are uncommon, but still a legitimate concern when storing hay. The gas doesn't need to be held. Just like oil or candles, only the gas will burn when mixed with enough oxygen. The seed will be constructed to keep the heat and gas in itself until a critical heat value is reached, opening the seed and setting fire to the shell and the gas. The shell should also burn so it'll last long enough to set the surroundings ablaze. $\endgroup$ – Trioxidane Dec 6 '20 at 10:38

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