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Okay, so I have a species of tree that's absolutely enormous, 1-5km tall when fully matured. Its immense size is supported by a large base, bark that incorporates a 2-d carbon lattice for strength (similar to graphene, carbyne and carbon nanotubes), and a fully functioning circulatory system to distribute nutrients to the top of the tree, all designed to overcome the limitations placed on its growth by gravity. These trees are obviously the kaiju of the plant world, and just like the Earth's biome could only feasibly support a handful of such giant creatures, I'd imagine only so many of these trees could exist on a given planet or landmass, and probably not enough to sustain a genetically diverse population.

That got me to thinking. How does this plant species reproduce?

Now, bear with me. I realize I'm no science or biology major and that I totally stole this idea from Starship Troopers, but could this tree's life cycle incorporate biological "eruptions" designed to fling seeds/spores as far as possible to cover a wider area?

I imagine it'd work something like this. After reaching adulthood, the tree begins to continuously build up pressure in its main chamber, or perhaps it begins converting some of its nutrients into a flammable explosive stored inside the trunk. It then periodically "erupts" in a series of small (relatively speaking) ejections that relieve pressure and fling its seeds with enough force to scatter them across the surface of the planet to seed areas hundreds or even thousands of miles away. After a certain number of these small eruptions, the planet is covered in the main tree's smaller, monozygotic offspring, and the tree begins nearing the end of its reproductive cycle. It then allows the pressure or the concentration of explosive fluid to build without erupting until it bursts in the largest eruption of its life, which kills the tree but sends a large seed hurtling not just into the atmosphere to cover the planet, but into space to seed the next planet it lands on.

Is this plausible? Is this mechanism viable and could such a large organism that flings its seeds/spores into space at escape velocity possibly exist?

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  • $\begingroup$ Regular trees can grow over 100m, i know of no hard limit. If the surface supports it, why not 1000m? Of course, the evolutionary pressure in that direction is simply nonexistant. But why couldn't you use a 50m tree for your explosive reproduction idea? And why not use regular fruits and birds to spread all over the planet? I see three crazy concepts with no logical connection. ;-) $\endgroup$ – Karl Sep 20 '16 at 1:51
  • $\begingroup$ @Karl The primary limit is how much work it takes to bring water up from the roots to the leaves. They can get to about 130m before it becomes an issue. $\endgroup$ – Cort Ammon - Reinstate Monica Sep 20 '16 at 3:46
  • $\begingroup$ @CortAmmon My latest knowledge is that biologist are still not sure how it works, and that there is a strong suspicion that there's an active transport mechanism involved after all. Do you know actual facts? $\endgroup$ – Karl Sep 20 '16 at 4:17
  • $\begingroup$ @Karl The study I quoted was from 2004. It's very plausible that the scientific community did not form a consensus behind that study, but it's been my go-to study on the topic for a while (as a layman -- not a professional in that field) $\endgroup$ – Cort Ammon - Reinstate Monica Sep 20 '16 at 5:05
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    $\begingroup$ Larry Niven's stage trees. Genetically engineered trees, produced by ancient alien technology, to grow into solid-fuel rockets, with multiple stages. Over hundreds of millions of years they spread their seeds across space & into many systems. One of the cute backstory features of Niven's Known Space series $\endgroup$ – a4android Sep 20 '16 at 8:35
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Getting into space is not easy. You will need to achieve escape velocity to get to another planet, so 11.186km/s. That's fast. You're going to need a lot of energy. 62MJ/kg to be specific. Fortunately, on a global scale, that much power isn't so bad. Hurricanes release 600000000MJ every second.

Getting those sorts of speeds is the tricky part. Your idea is basically an organic implementation of a space gun, so we can draw a lot of information from those studies. One of the major issues that shows up is that these speeds are very difficult to achieve in the atmosphere:

... these speeds are too far into the hypersonic range for most practical propulsion systems and also would cause most objects to burn up due to aerodynamic heating or be torn apart by aerodynamic drag. Therefore, a more likely future use of space guns would be to launch objects into near Earth orbit, from where attached rockets could be fired or the objects could be "collected" by maneuverable orbiting satellites.

Gee-forces would be quite intense too. The acceleration required by space gun is governed by $a=\frac{v_e^2}{2l}$, where $v_e$ is the escape velocity needed and $l$ is the length of the gun. Most space guns we look into are very long. Wikipedia gives an example of a 60km long one, and the acceleration experienced in that gun was in excess of 100g's over the ~10 second firing. Humans cannot survive those forces, so such cannons are certainly not for human consumption. However, if we assume $l=5km$ from your tree, the acceleration is a mighty 12500m/s^2, or 120 gees. Structural integrity under that kind of acceleration would be daunting, especially given that trees typically don't have nice smooth bores like a cannon.

Space is Hard - Scott Kelley

As for distributing seeds around the globe, a less ambitious endeavor, you could certainly use giant explosive eruptions for that. However, I'd like to offer a more subtle approach which you might consider:

Atmospheric Vortex Engine

The Atmospheric Vortex Engine is a theoretical approach to dumping heat out of a power plant into the stratosphere, but it could be highly applicable to your trees. The basic idea is to create a vortex which rises up into the upper atmosphere. If your tree could create such a vortex, it could loft its seeds into the jetstreams with little to no effort.

The Vortex Engine is still the subject of much debate. We don't have much experience generating such huge vortexes, but it might fit with your story well. And, if it fails, there's always nature's vortex engines:

Hurricane Fran

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  • $\begingroup$ I agree simple fluid compression will not get you to space, you would have to compress the fluid until it was practically a solid. $\endgroup$ – John Jun 21 '18 at 14:22
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Answer: this hypertree will reproduce by two means:

  • Fruit Birds will pluck up fruits and carry the seeds. A tree this big would make a perfect partner, it'd be a colony for all birds without interference from the landwalkers.

  • Spores A tree this tall is very likely to release seed-filled spores to be carried by the capricious winds. It is less efficient than birds, but it would add up to the reproduction possibilities

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