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Without magic, is it possible for a plant to channel light (all colors) to/through its roots?

What I'm thinking is having a giant cavern with a bunch of these plants above. The roots go down and cover the ceiling of the cave. When the sky is blue the roots either turn blue and/or give off a blue light. If there are clouds in the sky they are seen in the cave. In a way that's like a camera on the surface and a screen on the roots. Or have the whole plant change color, like a chameleon, to show what is above.

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  • $\begingroup$ this article says plants channel light into their roots. Don't know how reliable this is, but couldn't you just increase this effect? $\endgroup$ – Secespitus Jan 19 '17 at 21:03
  • $\begingroup$ I'm thinking of an answer along the lines of what a cuttlefish does. However, a cuttlefish is an intelligent carnivore with great utility for its color changing skills and the extraordinary capabilities of the cephlopod eye. The issues I keep running until is finding any utility for such capabilities for a tree. Autophores like plants typically don't need camera-grade eyes, and even when they can sense daylight, it is a very limited process. $\endgroup$ – Cort Ammon Jan 19 '17 at 21:18
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    $\begingroup$ @Cort, Could you make the plant like a Venus fly trap? With enough nutriets, the fly trap doesn't develop "petals(?)" To catch flies. But when nutrients aren't plentiful, it develops another method to get them. Perhaps the light emission could be a way to attract prey to catch them in the roots, somehow, and absorb nutrients from said prey. $\endgroup$ – Iter Jan 19 '17 at 21:32
  • $\begingroup$ @Iter Hmm... I may be able to work something like that! $\endgroup$ – Cort Ammon Jan 19 '17 at 21:34
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Without magic, the easiest way to achieve this would be for the roots to contain chemiluminescent substances. The leaves absorb energy from the sun, and the roots convert that energy back to light.

There are a number of issues:

  • It's slow - the roots would continue to glow long after the sky goes dark. They would continue to glow until the plant runs out of energy, unless there was some kind of signalling system, or a hormone released by the leaves that caused the roots to shut down.
  • It's monochromatic. The glow of the roots is dependent on the chemicals, not on the colour of the light shining on the plant. There could be multiple chemicals.
  • On a sunny day, most of the light comes from the sun (which is white, not blue). If you want to make a camera, you need a lens of some type. This can be gotten around -- you don't need one big lens, only little lenses on each tree, or even a pinhole lens. But then all the trees need to be pointing their cameras the same way.
  • It's costly for the plant. What benefit does the tree get from having glowing roots? It must be pretty important, since generating light this way uses lots of energy, and plants don't have lots of spare energy. Perhaps the glowing roots attract insects, and the tree gets essential extra nutrients as a carnivorous plant (like an upside-down sundew)
  • It's pretty dim, You can't read by the firefly light, The process of turning light into food, and food back into light is very inefficient (expect 99% wastage of energy in the process) This means the cave won't be lit up like the day.

There are real glowing mushrooms, and bioengineered plants that glow dimly. However the reality is a long way from a cave that reflects the sky.

The lens issue is the hardest to solve. That plants could have glowing roots is plausible. That a forest can cooperate to form a detailed image of the sky may require magic.

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    $\begingroup$ plant roots almost always have a symbiotic fungus that helps them absorb nutrients. maybe these long rooted plants have a bioluminescent fungus (or which there are many) as a symbiote. Weirdly it appears that the luminescence rarely serves a purpose it is just a side effect of how their metabolism works. en.wikipedia.org/wiki/List_of_bioluminescent_fungus_species $\endgroup$ – John Jan 19 '17 at 22:01
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    $\begingroup$ Good answer. Assuming these plants adapted to grow on top of caves perhaps the advantage of the light was to attract animals to the caves beneath. The animals would give off heat, produce food waste (and other waste) and, if predators, they might make it less likely birds would land close to eat the bulbs of the plants. $\endgroup$ – Lio Elbammalf Jan 19 '17 at 22:06
  • $\begingroup$ You could have a colony of different plants to create the desired multicolored effects, the way a monitor builds up colors from monochromatic cells. $\endgroup$ – PTm Jan 19 '17 at 22:55
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You could try something along the lines of a venus fly trap. Venus fly traps have modified leaves (the kind with "teeth" people often associate with the plant) when they can't get enough nutrients from the ground. When there's plenty of nutrients, those leaves don't even form.

As for your plants, you could have their roots capable of ensnaring prey and absorbing nutrients from said caught prey. The light, then, would act as a lure for prey. When there are plenty of nutrients in the ground, the roots would not have to dedicate energy to creating the chemicals needed to cause luminescence. But when nutrients are hard to come by, the lights go on!

Now, this would effect your ecosystem. You'd have to have life that would actually be caught by these plants. They can't have a system to catch prey if no prey exists. So, while you don't necessarily have to go into detail of creating a life form, you could briefly describe some "creature" being caught in the roots, obviously dead, looking as though drained. Or something like that, anyway.

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Take a look at marine mammals

As discussed by the other answers, everything takes energy, so if this evolves, there must be a good reason. My solution is camouflage.

enter image description here

Many aquatic creatures have bright undersides and dark backs. This means that creatures looking up at them from below may mistake them as being part of the rest of the sunlight they see - or from above, they may blend in with the seafloor.

Perhaps your plants started out on the surface of a body of water, or in the treetops, or on ledges, and most predators were below them. It would be evolutionarily advantageous to change root color throughout the day because it would fool predators into thinking they weren't there - or were something else - etc.

Other answers are correct - these lights will have to be dim, and complicated processes must produce them that may not be efficient - but that is true for all solutions to your problem. This just justifies how your plants evolved.

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You could have the plants costruct what would be, in essence, organic light guides.

Why would a plant evolve such a mechanism is a bit difficult to justify though. But the plants might have evolved to resist extremely hostile environments, where the "parent" plant in all likelihood dies and the "young" sprigs are kept safe underneath. The deeper they go, the safer they get, but of course they would get almost no light as soon as their shelter is more than a few millimeters deep.

Obviously most of the plants would have instead preferred to go the "deep hibernation" way.

Solutions such as transparent roots don't work very well, but said roots would have evolved to get hard, semitransparent excrescences similar to veins in order to safely bring light to the seeds in their bunkers, waiting for the conditions to be favourable once again. In time, these "crystal veins" would have become reasonably efficient light guides.

Something like this.

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