I'm building a world for an artistic project, and I'm struggling a bit with how the photosynthetic organisms would likely be different from Earth's plants. I'm not looking for wild idea generation, merely the plausible differences you might expect (i.e. predict) based on the much different environmental parameters.

Key Facts:

  • M-Dwarf Planet (3310K star)
  • Eccentric orbit combined with tidal resonance leads to zones on the planet which experience differing amounts of daylight per orbit. There is a "long day" zone in one hemisphere and a "long night" zone in the hemisphere opposite the long day zone. For example the long day zone gets up to 14-16 earth days of daylight, but only 13-11 earth days of night.

Other Basics:

  • Gravity is 75% Earth's
  • Thicker atmosphere
  • 2:1 tidal resonance (2 rotations per 27 Earth day orbit)
  • Long days and long nights due to a 27 Earth day diurnal cycle (sunrise to sunrise).
  • Planet is overall warm (freezing temps are rare). So no need to adapt to that.
  • No "seasons" (in the Earth sense) to speak of. The primary cycle in a location is the day/night cycle, which depends on the respective ratio of day/night.

First things first...the spectrum output of the star is far different than Sol's output, so the photosynthetic pigments that organisms use would be different. After some reading I've determined the color pallet of the "plants" on my world will largely be dark and desaturated purple, blue, and teal. In the zones of longer night the plants will largely look black. Photosynthesis will peak around 1,045nm, well into the near-infrared, though lower wavelengths of visible light will be utilized as well (orange, red).

Photosynthesis cycles will be different of course. Photosynthesis won't produce quite as much energy as it does in the sunniest areas on earth. Also there will be a longer period of activity and dormancy during the long days and nights.

But other than that...I'm not sure. I don't want the photosynthetic organisms to be too similar to Earth's, but I don't know enough about plant ecology to readily spin off ideas on what plausible differences are likely to evolve. What do you guys think? What am I missing besides the difference in pigmentation?


closed as too broad by Mołot, L.Dutch, sphennings, ShadoCat, John Feb 15 '18 at 1:02

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    $\begingroup$ Purely idea generation questions are often closed as too broad or primarily opinion based - evolution is hard to predict process that even hereon Earth created solutions we wouldn't imagine without seeing, and did not create things we believed we see. $\endgroup$ – Mołot Feb 14 '18 at 16:01
  • $\begingroup$ I don't think this would be purely option based. Based on the specified differences, it should be possible to formulate likely characteristics, which is far from opinion. For example, the plausible color of the plants depends on the available wavelengths of light, which isn't opinion. Speculative, yes, but opinion no. Evolution is highly constrained by the characteristics of the environment. It is the plausible adaptations to these constraining characteristics that I'm asking about. Hope that helps! $\endgroup$ – n_bandit Feb 14 '18 at 16:26
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    $\begingroup$ @n_bandit I'm asking because how is the answer not simply "anything you want?" Is there any criteria I might have missed for what makes an answer good? I don't really see any obvious relation between your parameters and how plants work tbo, but I'm also no expert. Just wondering $\endgroup$ – Raditz_35 Feb 14 '18 at 16:54
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    $\begingroup$ "What am I missing" is a very broad question it implies more brainstorming than answering, you might want to change it to laying out an scenario and flora (give some more detail about your plants) and asking if it is plausible, that can be answered and should not get closed. $\endgroup$ – John Feb 14 '18 at 16:56
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    $\begingroup$ @n_bandit There are many questions here about alien photosynthesis and the answer is always the same (simplified): We don't know, plants evolved randomly. I still think this is a good fit, you just have to live with people questioning it. Try the sandbox perhaps, it can help you ask a more precise question worldbuilding.meta.stackexchange.com/questions/4835/… . $\endgroup$ – Raditz_35 Feb 14 '18 at 17:01

There is no real reason to have any difference, there is nothing about your planet that earth plants do not already have to put up with in some environments. Vegetation color is due to quirk of evolutionary chance so you can make your plants whatever color you want as long as the light they absorb is actually present. without you coming up with specific adaptations there is not much of a question to answer.

  • $\begingroup$ Focusing on the physics of the day/night length isn't my intention, but since you've asked I've uploaded my diagram to this site (I don't know how long it'll host it for): i.imgur.com/7bmBbQe.png The planet has near zero axial tilt and is in 2:1 orbit/spin resonance. The difference in day/night is for a given point on the planet's surface, and is caused by the planet's orbital speed changing along the path of its eccentric orbit, per Newton's laws of motion. So the planet travels faster the closer it is to the star, but always maintains the same rate of rotation. $\endgroup$ – n_bandit Feb 14 '18 at 18:30
  • $\begingroup$ but day and night are still the same in that diagram, it can be long on a specific place on the planet, but the planet as a whole still experience 50% day 50% night. You really should include that diagram since the term hemisphere is not helpful to understanding what is happening, many will make the same mistake I did than think you were talking about north vs south hemisphere. $\endgroup$ – John Feb 15 '18 at 0:59

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