4
$\begingroup$

I would like my planet to be inhabitable by many species and humanoids. It has a cold climate than earth. I'd like the sky to be an yellowish pale orange. Would that change the color of grass or leaves as an overview?

$\endgroup$
5
  • 1
    $\begingroup$ why would your sky be yellow? Is it because of the atmosphere and how light is scattered by it (which is the reason our sky is blue), or is it because the star it orbits already emits a certain spectrum? $\endgroup$ May 24 at 10:17
  • $\begingroup$ It depends on the eyes of the viewer. What wavelenghts do their eyes detect and how do they perceive them? Color is all in the mind of the beholder. $\endgroup$ May 24 at 12:09
  • $\begingroup$ When you ask if changing the color of the sky would change the color of grass, do you mean that the sky was originally blue and then it became orange? If the sky was always orange, what is the meaning of the word "change"? (And why would you believe that on that alien world there is any grass? Grasses are a kind of plants which evolved here on Earth. Were they somehow transplanted on the alien world? Because the default position is that the life on the alien world is not related at all to the life on Earth; and even on Earth, grasses are late comers -- they only appeared in the Cretaceous.) $\endgroup$
    – AlexP
    May 24 at 12:12
  • 1
    $\begingroup$ Grass and leaves are (mostly) green because of chlorophyll. Unless the plants on your world use another chemical for photosynthesis, they will still be green. Given that the light coming from the sky is shifted towards the yellow, the grass and leaves may seem more yellow-green than blue-green. $\endgroup$ May 24 at 12:20
  • 1
    $\begingroup$ This question is asked often and the answer is always the same, Whatever you want it to be, plant color is not related to the color of the sky unless a wavelength is completely lacking. $\endgroup$
    – John
    May 25 at 20:26

4 Answers 4

4
$\begingroup$

Color is Surprisingly Unimportant

The plants we see today are green which is actually kind of weird because sunlight according to black body radiation should have a peak wavelength of roughly 500nm (https://hypertextbook.com/facts/2002/TahirAhmed.shtml) which is right on the edge between cyan and green, but the atmosphere filters out shorter wavelength light putting the peak more at a greenish yellow. That means plants in real life are reflecting the peak wavelength of light! Stranger still there are archaea (a very ancient, but still extant form of microorganism) with a very simple form of photosynthesis that uses purple pigment! This not only absorbs the peak band of energy, but is also likely an older form of photosynthesis! At the end of the day, the visible light specturm is only a tiny part of the overall specturm of light and the color of plants depends more on what works now than what's optimal. Leaves can also have pigments completly unrelated to photosynthesis. For example, where I live there are blue spruces which get their blue hue from the protective wax that covers their needles. Some trees have purple leaves (either year round or during autumn) from anthrocyanine which can act as a sort of sunscreen (ironic isn't it?) in very sunny environments or a deterent from pests. Nature plays it fast and loose when it comes to foliage and so can you!

$\endgroup$
2
$\begingroup$

If the plants absorb yellow light, you should remove that from the incoming light to get the color of the foliage. When in doubt, use black colored plants.

$\endgroup$
2
$\begingroup$

They will absorb the wavelengths that are the most steady and reliable

The green color of Earth plants seems strange at first, since it means they reflect the green wavelengths of light, which are the strongest wavelengths that reach the Earth's surface. For some time, it was believed that this was basically an accident; that plants which could absorb the green wavelengths would technically be superior but chlorophyll was "good enough".

However, it turns out that the evolutionary pressures on photosynthetic organisms are more nuanced than simply absorbing as much energy as possible. The issue is that while green wavelengths are abundant, they also fluctuate significantly over the course of a day, and the amount of green light hitting a plant will change a lot depending on whether it is in direct sunlight or shade.

Absorbing too much energy can be dangerous for an organism that is not prepared to manage it, resulting in free radicals and damaged tissues, and evolving to block out high-energy wavelengths will prevent it from absorbing them when they are weaker. Switching from one "mode" to another can be costly, so what an organism wants is not the strongest light, but the most reliable wavelengths, so that it gets a steady and predictable influx of energy that it can evolve to absorb efficiently.

On Earth, red light is scattered through the atmosphere, so it will hit a plant whether it is in direct sunlight or shade. And because the sky is blue, blue light will hit the plant regardless of where the sun is in the sky. So Earth plants evolved to absorb red and blue light, while reflecting the stronger but more volatile green light.

This same effect also predicts the color of other photosynthetic organisms on Earth, such as aquatic red and purple bacteria which tend to live at depths where blue or green light provide the most reliable source of energy.

So back to your question: since the sky is yellow (regardless of the position of the sun), plants will probably benefit most from absorbing yellow light, and they will also benefit from red for the same reason as on Earth. This means they will probably be blue.

$\endgroup$
1
$\begingroup$

the answer by @indigofenix is wonderful and i think fulfilled the needed answer. I'm only want to add this video by artifexian. this video talk about the correlation between the color of the sky and the color of the leaves of plants. i think this video could help you a lot in this topic.

$\endgroup$

Not the answer you're looking for? Browse other questions tagged .