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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?

n_bandit
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    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. – Mołot Feb 14 '18 at 16:01
  • 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! – n_bandit Feb 14 '18 at 16:26
  • What do things like global average temperatures have to do with how plants behave. Individual plants live very much localized in such a small area that such things don't matter. There isn't one way for biology to work. There isn't some predestined path evolution has to take. And on top of that, biology is incredibly complicated. You cannot simply ask "I change ten parameters about the planet, what will happen to one specific aspect of biochemistry?". You have to model how life developed on an alien world when we are not even sure about earth. How can any statement be proven wrong? – Raditz_35 Feb 14 '18 at 16:38
  • there are earth planets that live in far longer day and night cycles, arctic plants have to put up with this. – John Feb 14 '18 at 16:39
  • @Raditz_35 Proven wrong? I'm not sure I understand since my question is asking for suggested likely adaptations. There's nothing to prove wrong/right. As for the global temperatures...I just mentioned them so no one would make a suggestion based on an assumption of freezing temps during the long night. I would say the big difference planet wide (as far as flora are concerned) is the different wavelength output of the star, and the very different day/night cycle when compared to Earth. – n_bandit Feb 14 '18 at 16:46
  • You do not need to justify plant color with star output, plant color on earth is due to chance not solar output. Whatever color algae first gets incorporated in an symbiotic relationship will determine which color your plants are, on earth that happened to be blue/green algae. Plants on earth could just as easily be pink or blue. https://worldbuilding.stackexchange.com/questions/63259/what-colour-is-the-foliage-if-the-sky-is-violet/63264#63264 – John Feb 14 '18 at 16:47
  • @John Indeed they do! However, the light/dark cycle in the arctic is much different. For one thing it comes coupled with freezing temperatures and permafrost, for another it's much slower (365 day cycle as opposed to 27 "earth day" cycle). So I'm not sure if there are lessons I can pull from that example. But perhaps I'm wrong. Any specific adaptations you think might apply equally in this scenario? – n_bandit Feb 14 '18 at 16:49
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    @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 – Raditz_35 Feb 14 '18 at 16:54
  • @John Hmm...I agree in part. There is a large element of evolutionary capriciousness to the color of earth plants, but its not ALL random. For example, it might be unlikely that terrestrial earth plants adapted to canopy life would have turned out blue or red for example. This is because in order for the plant to be blue it would need to reflect blue and in order to be red reflect red. If the plant did either of these things, it would miss out on either the most energetic readily available photons (blue) or the the most plentiful photons (red). Any such plant could be outcompeted easily. – n_bandit Feb 14 '18 at 16:54
  • @John Concerning likely plant colors, I found this reference very helpful: https://www.ebscohost.com/uploads/imported/thisTopic-dbTopic-1033.pdf. Its from the NASA Goddard Institute for Space Studies. – n_bandit Feb 14 '18 at 16:55
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    "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. – John Feb 14 '18 at 16:56
  • @Raditz_35. Hm. Maybe I haven't phrased my question well. Sure. There's definite criteria. Basically, if the answer could reasonably be phrased in this form: "Plants on your world might be likely to evolve _____ because of _____" then it's likely a good answer. For example the color info I supplied I consider a good partial answer, since it is a LIKELY adaptation we could predict. Then again...maybe this isn't the right forum for this sort of question? – n_bandit Feb 14 '18 at 16:58
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    @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 https://worldbuilding.meta.stackexchange.com/questions/4835/sandbox-for-proposed-questions . – Raditz_35 Feb 14 '18 at 17:01
  • @John Good suggestion. The problem is I don't even know where to start, other than "Like earth plants but different pigments." I don't know enough about plants to even guess at what would likely be different. I'm hoping someone can outline the broadest strokes. Kind of like it I said "High gravity world, what are the animals like?" we could come up with a half-dozen likely adaptations: sturdier limbs, more limbs, less flight, etc. – n_bandit Feb 14 '18 at 17:01
  • Plants already ignore the vast majority of the available energy from the sun (500-600nm), please look at the answers to the linked question, plants only utilize the ends of the spectrum because the abundant middle was already taken when the bacteria that would later become plant evolved. https://worldbuilding.stackexchange.com/questions/63259/what-colour-is-the-foliage-if-the-sky-is-violet/63264#63264 – John Feb 14 '18 at 17:01
  • There is no real reason for them to be different than earth plants so you need a to define a difference to be evaluated, otherwise you are just asking us to brainstorm for you which is discouraged. You might want to start by asking if your plant is plausible becasue variation from pole to equatorial temprature is due to curvature of the planet and the location of continents and thus can't be changed much. there is also no way to get different length days and nights and not have seasons. both are caused by having a tilted axis. – John Feb 14 '18 at 17:06
  • @John Difference longitudes on the planet will have different day/night ratios due to the combination of 2:1 rotation/orbit resonance and orbital eccentricity. There is no axial tilt. On a world like this Season = Time of Day. Length of Season = Day/Night Ratio at that longitude. There is no separate season and day cycles. They are one and the same in this type or planet. I don't have a good reference for this, but I've drawn out the diagrams and done the calculations. It's accurate. – n_bandit Feb 14 '18 at 17:17
  • @John Hmm...if you think there is no reason for a difference, then that is a good answer! That might be the case. I wanted to know what I'm missing. Perhaps I'm not missing anything, and the light spectrum is it when it comes to big differences. – n_bandit Feb 14 '18 at 17:23
  • I'm sorry to have to vote to close this question but instead of listening to the comments people have made here and working to make your question better, you seem to be more interested in arguing with the commenters. We aren't trying to disparage you or shut you down, we are trying to help you ask better questions that fit this board. – ShadoCat Feb 14 '18 at 18:43

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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.

John
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  • 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): https://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.

     – n_bandit Feb 14 '18 at 18:30
  • 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. – John Feb 15 '18 at 00:59