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Chemoautotroph Flora

In a world where there is not much sunlight, I still want to have life. Specifically, I want to capitalize on chemoautotrophs so much that the alien schoolchildren learn something like "the source of life is volcanic vents" and flora which use photosynthesis is considered the odd method of deriving energy for life.

What properties would you expect in chemoautotrophic flora? Specifically:

How would the common root/stem/leaf pattern we know in most plants today be altered? What are likely energy sources for chemoautotrophic flora? (We need not limit ourselves to aquatic vent communities.)

Some relevant definitions:

Chemoautotroph: an organism which obtains energy via the oxidation of inorganic compounds, but not using photosynthesis

Flora: plant life lacking the power of locomotion

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    $\begingroup$ Absent aquatic vents, I'm not sure how you'd deliver energetic chemicals reliably enough for plants (or animals) to grab them continuously. Once a chemical that's at a higher energy level is processed, it's done and no good to any other life-form. You'll need a constant stream of higher energy chemicals delivered. $\endgroup$ – user3082 Feb 25 '15 at 16:17
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I think that bacteria are intrinsically better-suited to such environments - by default, there really isn't a "metal-cycle" in the same way as a "water cycle" to supply the raw ingredients.

But plants like this would be amazing. You could have junkyard-plants that grow in caves filled with rusty cars and turn them into...tomatoes or something. And heaps of rust.

You still need sugar. Ultimately, your plants need carbon, hydrogen, and oxygen. The exotic elements seem to come in along with one of those three elements.

So to answer the question about environment:

  • A warm environment to mix the required materials (and energy to start the reactions)
  • An environment that can move the materials to where the plant needs them, naturally. This implies a high-density environment.
  • The waste also needs to be removed. Living in a pile of sulfur really isn't that pleasant. Terrestrial plants produce gases as the byproduct of their reactions, which are moved away from the plant by nature. Plants that produce piles of rust or sulfur will need a similar mechanism to keep the area clean.
  • A steady supply of whatever materials they need is helpful
  • A supply of water or air to bring in the H2O, CO2, or whatever hydrocarbon source is needed.

The most logical place to find these things is an aquatic environment. Maybe a hot spring or volcano...oh wait, what about a hydrothermal vent?

But it's also possible that the roles could be reversed - the "leaves" gather the materials, but chemosynthesis and waste production occurs in the roots, where it is carried away by ground water. In that case, you'd need some noxious metallic gas floating around, like maybe next to a volcano.

Finally, if all the need materials are available in the ground, you might see very spidery root systems, with only minimal structures to support flowers/fruits above ground for reproduction.

In any case, not somewhere readily habitable by humans.

What would the plants look like? I think you'd still have leaf structures, but they'd be more mesh than solid material, with lots of frills to grab the (fill in element here). Roots would probably be similar.

Plants would not be green. Most likely you'd see rust-colors, and the plants would "blanch" when they run low on materials.

Presumably there would be an ecosystem that would use the plant waste.

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I think such plants would have no use for leaves. Leaves are basically solar energy collectors, and since your plants do not do photosynthesis, they have no use for them. I'd expect all the energy production to happen inside the roots. So the roots would be the most important parts of the plant; I could even imagine that some plants would never actually leave earth (exposure gives risk for little reward).

Indeed, we already have organisms which share such characteristics, although they don't live off volcanic activity, but off organic material: Fungi. So I'd expect chemoautotrophic plants to look and live very similar to fungi/mushrooms. Of course you'll also have real mushrooms because there will be organic material to decompose, but I guess you'd be hard pressed to optically distinguish both; the main way to distinguish them would be to watch where they live.

With a dense root/mycelium network, the plants could also expand a bit beyond the volcanic sources, by carrying the raw material along the network. Since the places would be filled with plants, this might give a competitive advantage.

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