So I'm currently designing an alien habitable planet that orbits a star similar to our Sun. Assuming that the composition of the planet's atmosphere, as well as its pressure, are similar to the ones on Earth, would plants on this planet have any other color than green?

  • $\begingroup$ @T.J.L. Because it's all on the Wikipedia entry on Chloroplast. And I have already provided an answer along these lines. With a picture of a purple-leaved Prunus cerasifera var. pisardii. $\endgroup$ – AlexP Feb 20 '19 at 16:54
  • $\begingroup$ Why wouldn't a planet similar to Earth in so many ways have the same range of colors in plants that Earth currently has? You haven't mentioned any parameter that is different from Earth. $\endgroup$ – Cyn says make Monica whole Feb 20 '19 at 18:12
  • $\begingroup$ This answer is quite comprehensive on the matter: worldbuilding.stackexchange.com/questions/11562/… $\endgroup$ – Arkenstein XII Feb 20 '19 at 19:28
  • $\begingroup$ @ArkensteinXII that's a good question you linked to and one that makes sense. I get how having different parameters produces different results. What I don't understand is how you can have different results with the same parameters. Unless you think the fact that most (not all) plants are green on Earth is random chance. $\endgroup$ – Cyn says make Monica whole Feb 20 '19 at 22:07
  • $\begingroup$ @Cyn It's unfortunate that we have a sample size of one. We can make assumptions about why Earth's flora are green, but we have no other examples of flora against which to test our hypotheses. Any speculations we do have on the matter tend to drift toward 'just-so' stories. $\endgroup$ – Arkenstein XII Feb 20 '19 at 22:17

Plants come in many colours anyhow, Chlorophyll making the base colour green for most, other pigments occur naturally too; Carotenoids - ranging in colour from yellow/brown to dark green, Betalain - red and yellow, Anthocyanins - red purple or blue.

Chlorophyll is of course green but if your plants used other compounds instead they could be different colours.

it has an appreciable detected emission for excitation wavelengths between 470 nm and 650 nm (with a peak at 570 nm)

  • Melanins (brown, red) It has a wide absorption spectrum covering the whole of visible light into the ultraviolet and can break down water, and is thousands of times more efficient at it than chlorophyll.

it is considered the world's most important reaction since it is the beginning of the food chain. Therefore, a plant without water will not hatch, since the free chemical energy that is released with the breakdown of the molecule of water is essential to boost consequential reactions

The chemistry of photosynthesis is driven by chemical reactions - which are driven by shifting electrons about between atoms/molecules - sometimes because that's the way they want to go - sometimes because they're given a kick from outside (photons) - essentially a gradient.

Nanotechnology to generate electricity - electron/proton gradient pumps have evolved in the above forms. They have also been created by people in so many forms: Honeycomb graphene structures, copper indium selenide sulphide quantum dots, graphene sheets, graphene coated with zinc nanowires. If we can make it, who's to say it can't evolve in nature and better. Curiousley, many of them appear blue/black.

Ways to produce colour effects without pigment such as by constructive and destructive interference on a nano-scale such as in butterfly wings could evolve.

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Credit Kevin Walsh

In fact they have:

Pollia condensata

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Wikipedia 2019 CCSAL Licence

Your options are open wide.


There are multiple theories, why clorophyll is dominating on Earth. Source


One theory is that early oceans were filled with purple microbes called archaea. The light-sensitive molecule in these microbes is called retinol, which absorbs green light and reflects red and violet light, which makes them appear purple. So parts of the earth could have looked purple! All the green light was taken by archaea, so chlorophyll had to make do with blue and red light. However, chlorophyll-based life became much more dominant because even though it uses less of the light spectrum, chlorophyll is much more efficient.


Another theory is that absorbing too much light could damage the plant more than it would help, much like how when we get too much sun, we get a sunburn. So it could be beneficial that the plants are getting less light.

So I assume, that if everything is similar (distance to sun too), then sooner or later clorophyll is going to take over. But, if the distance to sun is different, or temperature is different, there might be a need for more efficient photosynthesis - it could work with different molecules on different wavelengths.

  • $\begingroup$ the big problem with the second idea is the plants could just produce less chlorophyll. $\endgroup$ – John Feb 18 at 5:42

Most likely yes.

One of the big factors that give (most) Earth plant-material it's predominant green color is the chemical Chlorophyll. This is a major component of the chemical complex that allows a plant to absorb solar energy.
On a different planet, with total different biology the odds are high that "plants" or their local equivalent use something entirely else and therefore may have radically different colors even if everything else is much the same as on Earty.

E.g. If you local plant life, due to its chemical/biological composition, is most efficient in absorbing energy in the blue and UV part of the spectrum, it wouldn't make much evolutionary sense for those plants to have blue/UV colors as every bit of light in those colors reflected isn't benefiting the internal workings of the plant. So those plants would probably reflect anything BUT blue/UV and look to be yellow/orange/red in color.


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