13 ms·

Why Are Plants Green? To Reduce the Noise in Photosynthesis

247 points by theafh 6y ago

russfink 6y ago
Why wouldn't fluctuations of sunlight that cause instability in the green spectrum also cause instabilities in the red and blue spectra?
- uj8efdkjfdshf 6y ago
  I think the point is that since the power available at these wavelengths vary sharply with frequency in these regions of the solar spectrum, the plant can easily compensate for brightness fluctuations in these portions of the spectrum with minor tweaks to the target wavelength of the relevant photosystems
  - londons_explore 6y ago
    I'd this is the case, it's a shame the article didn't mention it. It makes sense the changing environmental conditions for a molecule could affect the wavelengths of light it absorbs (for example, pH, temperature, etc), but I'm not sure this has been demonstrated for plant pigments?
  - Sniffnoy 6y ago
    I'm confused though -- how can the plant possibly vary this?
    - danbruc 6y ago
      In principle plants have several different variants of the light absorbing molecules with different absorption spectra but I don't know how this would actually be regulated. But it is certainly imaginable that plants vary the relative abundance of the different light absorbing molecules or their efficiencies and this could be more or less automatic because of varying conditions like pH or whatnot that affects efficiency or lifetime of the molecules with a simple feedback mechanism or it could be actively regulated by a more complex feedback loop.
- floatrock 6y ago
  > It might be highly efficient to specialize in collecting just the peak energy in green light, but that would be detrimental for plants because, when the sunlight flickered, the noise from the input signal would fluctuate too wildly for the complex to regulate the energy flow. > Instead, for a safe, steady energy output, the pigments of the photosystem had to be very finely tuned in a certain way. The pigments needed to absorb light at similar wavelengths to reduce the internal noise. But they also needed to absorb light at different rates to buffer against the external noise caused by swings in light intensity. The best light for the pigments to absorb, then, was in the steepest parts of the intensity curve for the solar spectrum — the red and blue parts of the spectrum. I admit there's a bit of a jump there (gotta read the actual article, not the journalist retelling I suppose), but I assume the gist of the math is something like this: Lets say direct green light delivers a maximum 100 "units of photo-energy" -- gonna play loose with the physics to demonstrate the math. When a cloud passes over it, lets say the intensity drops to only 75%. Lets also say for now we always convert the energy at 100% efficiency. So with green light, your 100 units of energy drops by 25 units with each passing cloud. Now lets say blue light delivers only 80 units of energy. When that same cloud passes over, 80 * 75% = 60 units of energy, or a drop of 20 units. So, if your process is sensitive to changes in absolute energy, you would rather have a swing of 20 units for every passing cloud than a swing of 25 units. Yeah, you might get less absolute energy (60 units rather than 75), but if the cost of energy swings in your process was very high, the tradeoff might be worth it. You could also play with the efficiency-of-conversion (ie have higher conversion efficiency at the lower-swing points) for some fun second-order effects. This is just a toy example of what the underlying dynamics could be. Gotta read the actual paper to understand the actual model they developed. https://arxiv.org/pdf/1912.12281.pdf https://arxiv.org/pdf/1912.12281.pdf
  - wcoenen 6y ago
    > Now lets say blue light delivers only 80 units of energy. When that same cloud passes over, 80 * 75% = 60 units of energy, or a drop of 20 units. So, if your process is sensitive to changes in absolute energy, you would rather have a swing of 20 units for every passing cloud than a swing of 25 units. That's not exactly it. The idea is that the blue light absorption can be tuned (presumably by shifting the absorbed wavelengths by a few nanometer) to compensate for external changes. So if the overall light intensity drops 1%, the system responds by shifting the absorbed spectrum to get 1% more power. This only works in parts of the solar spectrum where power varies sufficiently versus wavelength, hence the preference for blue and red.
- FriedPickles 6y ago
  They do. The paper's point is that plants want to choose two wavelengths with different amounts of average power. This gives the plant a window to tune within to get the desired amount of output power. If the total illumination drops, the plant compensates by tuning more towards the high power wavelength, and vice versa. But the paper makes the point that the tuning mechanism isn't perfect due to internal noise. If the power level difference between the two input wavelengths is too great, then the random fluctuation of the tuning mechanism will itself create a lot of noise in the output. So basically there's an optimal value for the difference of average power between the two wavelengths. Now, why the plant doesn't absorb the peak green wavelength and the closest wavelength whose power is exactly the optimal difference less was unclear to me. I think the idea was that the plant also wants to minimize the wavelength difference, and a given power delta can be achieved with less difference in wavelength in the steeper sloping sections of spectrum power graph.
rkwasny 6y ago
Related, one of my favourite videos: Richard Feynmann explains fire: https://www.youtube.com/watch?v=N1pIYI5JQLE https://www.youtube.com/watch?v=N1pIYI5JQLE
SeriousM 6y ago
Finally a clickbait with explanation!
- 42droids 6y ago
  Wanted to say the same.
  - 42droids 6y ago
    Ppl who downvote comments like these are responsible for killing any joy and fun on the internet.
    - hutzlibu 6y ago
      Your fun and joy definition might not meet the definition of others. I for example do not enjoy metoo comments. If you do, you are likely a minority.
      - IncRnd 6y ago
        You started off well, but you ended with a logical fallacy.
        hutzlibu 6y ago
        Why? I shared my experience. Allmost no one I know enjoys these comments. Wheres the fallacy?
        IncRnd 6y ago
        You started out sharing your experience, yes, but that was not your last sentence. The fallacy is fallacy of composition, one of the forms of illicit transference. Another way to phrase that is you formed a hypothesis that you assumed to be true.
        6y ago
OrangeKnucles 6y ago
But shade affects light of all wavelength. Why would only absorbing red or blue light be better?
raxxorrax 6y ago
Some trees and plants that are still rebellious about this: https://www.ornamental-trees.co.uk/images/cercis-canadensis-merlot-p1128-7419_image.jpg https://www.ornamental-trees.co.uk/images/cercis-canadensis-... Of course those also have chlorophyll, but the color is overridden by other color particles. Sadly we have no blue trees. We have blue flowers though and it would probably be possible to create one. That would be so awesome.
- MarkSweep 6y ago
  A blue spruce is a fairly blue tree: https://en.m.wikipedia.org/wiki/Blue_spruce https://en.m.wikipedia.org/wiki/Blue_spruce
  - bregma 6y ago
    Blue spruce is actually pretty darn green, but its needs have a waxy coating that alters our perception of the colour of the underlying tissue. New needles, and needles you scrape with your fingernails, reveal their true green colour. A waxy coating is a strong selector for survival in an environment where preventing evaporation is a must, such as locations in which the ambient temperature drops below the freezing point of water for much of the year.
    - SECProto 6y ago
      Do black spruce have a waxy coating? They certainly don't appear blue, and they thrive in locations with much colder winters than the blue spruce.
      - piva00 6y ago
        As far as I know all coniferous (Pinophyta) have waxy coatings, black spruces are a species of Pinophyta so I'd assume they do. I might be wrong, I'm no botanist.
    - dTal 6y ago
      Isn't that a little like saying that a shiny red sports car is actually metallic gray, but it has a coating that alters our perception of it so that it appears red to our eyes? Color is what we perceive, nothing else. If it looks blue, it is blue.
stpedgwdgfhgdd 6y ago
The same applies to software development; local optimization does not weigh up against stability across the entire supply chain.
dvh 6y ago
I thought plants are green because sun is green. Edit: not sure about down votes, sun has peak in green spectrum. Our eyes are most sensitive to green, plants are green to utilize it as well.
- laszlokorte 6y ago
  If they would utilize the green light they would not reflect it - so should exactly not be seen as green by your eyes.
cortic 6y ago
I was really looking forward to reading this but its a bit of a disappointment. First, green does not have the most energy of the visual spectrum, Blue, or more specific Violet does; https://socratic.org/questions/5348556b02bf347bedff8fed https://socratic.org/questions/5348556b02bf347bedff8fed Second the noise difference from 10% of the green would be negligible compared to the energy we are talking about. Also how does a plant regulate this 'noise'? The only logical explanation would be expand into the green in dark and out of it in light, but they have shown no mechanism for a plant to do that. Sorry to say that after that fairly long winded article i have come to the conclusion we still don't know exactly why plants aren't all black. Edit; Thinking about this more, maybe Chlorophyll a and Chlorophyll b take inverted wavelengths of light to produce a rectification effect..? Its interesting, but even if that were true, it would not explain the gap at green. 2nd Edit; I stand corrected, considerably more green light make it through the atmosphere thank you for the information spacemark.
- alanbernstein 6y ago
  The "most energy" statement isn't about the frequency of light, it's about the power output of the sun, which peaks around green.
  - jiehong 6y ago
    That power output really is the area under the curve, in which case most of the sun's energy is in the infrared, actually.
    - alanbernstein 6y ago
      Sure. But the peak is around green, which is the point of the article and the answer to parent's question.
- deleted 6y ago
  [deleted]
- spacemark 6y ago
  >First, green does not have the most energy of the visual spectrum, Blue, or more specific Violet does The article is correct. Blue photons have more energy, you're right. But more green photons are emitted by the sun, and even more reach the ground through the atmosphere than blue, so the total energy from green photons is significantly greater. Google blackbody spectrum. https://en.wikipedia.org/wiki/File:Wiens_law.svg https://en.wikipedia.org/wiki/File:Wiens_law.svg https://lh3.googleusercontent.com/proxy/eDhfILMl70XZ-WUchpgoEQn77K7dvrZZg2iY5F4vaXnHE85OCjrWZC3EHjvMRU6FmW9bNSZNHLvlKlO_uYfLJgO7DRO0iAzsTRBc https://lh3.googleusercontent.com/proxy/eDhfILMl70XZ-WUchpgo...
jonplackett 6y ago
I always just assumed there wasn't much green light, so plants optimised for the rest of the spectrum: The sky is blue, the sun is orangey. Where's all this green light I'm missing?
- alanbernstein 6y ago
  Look at a graph of the spectral power output of the sun, you'll see that it peaks around green.
- sp332 6y ago
  Your green receptors overlap with red, and also a little with blue. There is no single wavelength of light that only stimulates your green photoreceptors without also setting off red or blue ones. https://en.wikipedia.org/wiki/Color#/media/File:Cones_SMJ2_E.svg https://en.wikipedia.org/wiki/Color#/media/File:Cones_SMJ2_E...
- colanderman 6y ago
  The sun is actually green (that is, is approximated by a black body emitter with a peak in the green region of the visual spectrum, see [1]). Its light appears white because that is how we are conditioned evolutionarily. ("True" white -- i.e. equal spectral energy -- appears blue-grey to us.) The sun "looks" orange because when you can look at it (sunrise/sunset), its light is heavily filtered by the atmosphere. [1] https://qph.fs.quoracdn.net/main-qimg-f9bc312e4d114e9e32a62714c36580aa https://qph.fs.quoracdn.net/main-qimg-f9bc312e4d114e9e32a627...
- projektfu 6y ago
  Orange is red and green. The intensity we perceive is also not the absolute intensity of that part of the spectrum. Neither is the luminosity equivalent to the power (as in energy over time).
hawktheslayer 6y ago
I might just use this trick of nature to inform how I manage my staff at work. We spend so much time trying to maximize efficiently, but perhaps at the cost of stability.
- deeweebee 6y ago
  This is the nerdiest sentence I’ve seen today. Dang!
throwaway_USD 6y ago
My understanding of the evolution of Earth flora is that prior to plants being green, the dominant plant life was red (think of red algae blooms) and that the current dominant green plant life likely evolved to use different photons along the EM spectrum where there was less competition. Funny enough as I understand visible light and the EMR spectrum there is no "green" (color/wave length/energy) rather the color green is a construct originating not in the light spectrum but in the mind of the observer.
- andrewflnr 6y ago
  I was thinking about the same hypothesis but IIRC it was highly speculative, with the main evidence for it simply being that modern plants evolved to use those other photosynthesizers' castoffs. We may not need that hypothesis anymore if we have a solid reason to avoid green anyway.
- Zaak 6y ago
  There is a range of wavelengths of light that humans perceive as green. The same is true for every color that is part of the rainbow. In contrast, the "pure purples" do not appear in the rainbow, and there is no single wavelength of light that humans perceive as purple (it requires red light plus blue light).
  - Balgair 6y ago
    The perception of color is a pretty wild area of science. Colors seem to be culturally dependent. In that, people literally cannot see the difference between blue and green if their language does not have words to distinguish them. Even when big rewards are given for the 'correct' answer. Colors also follow certain patterns, with colors like blue being the last to be named in a culture. https://www.youtube.com/watch?v=gMqZR3pqMjg https://www.youtube.com/watch?v=gMqZR3pqMjg Fun fact, the color blue does not appear at all in the Iliad, Homer describes the ocean as wine, despite the stunning blue colors of grecian seas.
    - sergeykish 6y ago
zadkey 6y ago
Why are some plants purple like tradescantia pallida?
Chris2048 6y ago
But, why do plants need a regular amount of light energy? Can't a black plant just absorb everything available?
odomojuli 6y ago
The color of plants and the statistics of light is fascinating. Tangentially related, I was developing a CV app for farmers in an early stage weed startup right before legalization in California so they could monitor analytics on the health of their sprouts as well as identify strains. The camera conditions were all over the place and data preprocessing stage was an absolute nightmare. We tried everything from filters to background removal, augmentation techniques through transformations, noise induction for generalization - nothing really improved the baseline models because the photos honestly sucked. Farmers ignored our guidelines on lighting and framing and format and kept sending in inconsistent garbage. I had a eureka moment. What if we sent each of the farmers a little piece of square cardboard painted magenta? The idea was that the increase in contrast would allow us to process the leaf contour a little bit better. The fact that the card was square meant some farmers even took the time to take the plant indoors so they could frame it better within the edges. Data quality improved dramatically. It worked. Unfortunately legalization did not work out as we planned, farmers disappeared and the market was monopolized by corporations, there wasn't any interest in helping develop strains locally.

247 points by theafh 6y ago

Why wouldn't fluctuations of sunlight that cause instability in the green spectrum also cause instabilities in the red and blue spectra?

uj8efdkjfdshf 6y ago
I think the point is that since the power available at these wavelengths vary sharply with frequency in these regions of the solar spectrum, the plant can easily compensate for brightness fluctuations in these portions of the spectrum with minor tweaks to the target wavelength of the relevant photosystems
- londons_explore 6y ago
  I'd this is the case, it's a shame the article didn't mention it. It makes sense the changing environmental conditions for a molecule could affect the wavelengths of light it absorbs (for example, pH, temperature, etc), but I'm not sure this has been demonstrated for plant pigments?
- Sniffnoy 6y ago
  I'm confused though -- how can the plant possibly vary this?
  - danbruc 6y ago
    In principle plants have several different variants of the light absorbing molecules with different absorption spectra but I don't know how this would actually be regulated. But it is certainly imaginable that plants vary the relative abundance of the different light absorbing molecules or their efficiencies and this could be more or less automatic because of varying conditions like pH or whatnot that affects efficiency or lifetime of the molecules with a simple feedback mechanism or it could be actively regulated by a more complex feedback loop.
floatrock 6y ago
> It might be highly efficient to specialize in collecting just the peak energy in green light, but that would be detrimental for plants because, when the sunlight flickered, the noise from the input signal would fluctuate too wildly for the complex to regulate the energy flow. > Instead, for a safe, steady energy output, the pigments of the photosystem had to be very finely tuned in a certain way. The pigments needed to absorb light at similar wavelengths to reduce the internal noise. But they also needed to absorb light at different rates to buffer against the external noise caused by swings in light intensity. The best light for the pigments to absorb, then, was in the steepest parts of the intensity curve for the solar spectrum — the red and blue parts of the spectrum. I admit there's a bit of a jump there (gotta read the actual article, not the journalist retelling I suppose), but I assume the gist of the math is something like this: Lets say direct green light delivers a maximum 100 "units of photo-energy" -- gonna play loose with the physics to demonstrate the math. When a cloud passes over it, lets say the intensity drops to only 75%. Lets also say for now we always convert the energy at 100% efficiency. So with green light, your 100 units of energy drops by 25 units with each passing cloud. Now lets say blue light delivers only 80 units of energy. When that same cloud passes over, 80 * 75% = 60 units of energy, or a drop of 20 units. So, if your process is sensitive to changes in absolute energy, you would rather have a swing of 20 units for every passing cloud than a swing of 25 units. Yeah, you might get less absolute energy (60 units rather than 75), but if the cost of energy swings in your process was very high, the tradeoff might be worth it. You could also play with the efficiency-of-conversion (ie have higher conversion efficiency at the lower-swing points) for some fun second-order effects. This is just a toy example of what the underlying dynamics could be. Gotta read the actual paper to understand the actual model they developed. https://arxiv.org/pdf/1912.12281.pdf https://arxiv.org/pdf/1912.12281.pdf
- wcoenen 6y ago
  > Now lets say blue light delivers only 80 units of energy. When that same cloud passes over, 80 * 75% = 60 units of energy, or a drop of 20 units. So, if your process is sensitive to changes in absolute energy, you would rather have a swing of 20 units for every passing cloud than a swing of 25 units. That's not exactly it. The idea is that the blue light absorption can be tuned (presumably by shifting the absorbed wavelengths by a few nanometer) to compensate for external changes. So if the overall light intensity drops 1%, the system responds by shifting the absorbed spectrum to get 1% more power. This only works in parts of the solar spectrum where power varies sufficiently versus wavelength, hence the preference for blue and red.
FriedPickles 6y ago
They do. The paper's point is that plants want to choose two wavelengths with different amounts of average power. This gives the plant a window to tune within to get the desired amount of output power. If the total illumination drops, the plant compensates by tuning more towards the high power wavelength, and vice versa. But the paper makes the point that the tuning mechanism isn't perfect due to internal noise. If the power level difference between the two input wavelengths is too great, then the random fluctuation of the tuning mechanism will itself create a lot of noise in the output. So basically there's an optimal value for the difference of average power between the two wavelengths. Now, why the plant doesn't absorb the peak green wavelength and the closest wavelength whose power is exactly the optimal difference less was unclear to me. I think the idea was that the plant also wants to minimize the wavelength difference, and a given power delta can be achieved with less difference in wavelength in the steeper sloping sections of spectrum power graph.

rkwasny 6y ago

Related, one of my favourite videos: Richard Feynmann explains fire: https://www.youtube.com/watch?v=N1pIYI5JQLE https://www.youtube.com/watch?v=N1pIYI5JQLE

SeriousM 6y ago

Finally a clickbait with explanation!

42droids 6y ago
Wanted to say the same.
- 42droids 6y ago
  Ppl who downvote comments like these are responsible for killing any joy and fun on the internet.
  - hutzlibu 6y ago
    Your fun and joy definition might not meet the definition of others. I for example do not enjoy metoo comments. If you do, you are likely a minority.
    - IncRnd 6y ago
      You started off well, but you ended with a logical fallacy.
      - hutzlibu 6y ago
        Why? I shared my experience. Allmost no one I know enjoys these comments. Wheres the fallacy?
        IncRnd 6y ago
        You started out sharing your experience, yes, but that was not your last sentence. The fallacy is fallacy of composition, one of the forms of illicit transference. Another way to phrase that is you formed a hypothesis that you assumed to be true.
        6y ago

OrangeKnucles 6y ago

But shade affects light of all wavelength. Why would only absorbing red or blue light be better?

raxxorrax 6y ago

Some trees and plants that are still rebellious about this: https://www.ornamental-trees.co.uk/images/cercis-canadensis-merlot-p1128-7419_image.jpg https://www.ornamental-trees.co.uk/images/cercis-canadensis-... Of course those also have chlorophyll, but the color is overridden by other color particles. Sadly we have no blue trees. We have blue flowers though and it would probably be possible to create one. That would be so awesome.

MarkSweep 6y ago
A blue spruce is a fairly blue tree: https://en.m.wikipedia.org/wiki/Blue_spruce https://en.m.wikipedia.org/wiki/Blue_spruce
- bregma 6y ago
  Blue spruce is actually pretty darn green, but its needs have a waxy coating that alters our perception of the colour of the underlying tissue. New needles, and needles you scrape with your fingernails, reveal their true green colour. A waxy coating is a strong selector for survival in an environment where preventing evaporation is a must, such as locations in which the ambient temperature drops below the freezing point of water for much of the year.
  - SECProto 6y ago
    Do black spruce have a waxy coating? They certainly don't appear blue, and they thrive in locations with much colder winters than the blue spruce.
    - piva00 6y ago
      As far as I know all coniferous (Pinophyta) have waxy coatings, black spruces are a species of Pinophyta so I'd assume they do. I might be wrong, I'm no botanist.
  - dTal 6y ago
    Isn't that a little like saying that a shiny red sports car is actually metallic gray, but it has a coating that alters our perception of it so that it appears red to our eyes? Color is what we perceive, nothing else. If it looks blue, it is blue.

stpedgwdgfhgdd 6y ago

The same applies to software development; local optimization does not weigh up against stability across the entire supply chain.

dvh 6y ago

I thought plants are green because sun is green. Edit: not sure about down votes, sun has peak in green spectrum. Our eyes are most sensitive to green, plants are green to utilize it as well.

laszlokorte 6y ago
If they would utilize the green light they would not reflect it - so should exactly not be seen as green by your eyes.

cortic 6y ago

I was really looking forward to reading this but its a bit of a disappointment. First, green does not have the most energy of the visual spectrum, Blue, or more specific Violet does; https://socratic.org/questions/5348556b02bf347bedff8fed https://socratic.org/questions/5348556b02bf347bedff8fed Second the noise difference from 10% of the green would be negligible compared to the energy we are talking about. Also how does a plant regulate this 'noise'? The only logical explanation would be expand into the green in dark and out of it in light, but they have shown no mechanism for a plant to do that. Sorry to say that after that fairly long winded article i have come to the conclusion we still don't know exactly why plants aren't all black. Edit; Thinking about this more, maybe Chlorophyll a and Chlorophyll b take inverted wavelengths of light to produce a rectification effect..? Its interesting, but even if that were true, it would not explain the gap at green. 2nd Edit; I stand corrected, considerably more green light make it through the atmosphere thank you for the information spacemark.

alanbernstein 6y ago
The "most energy" statement isn't about the frequency of light, it's about the power output of the sun, which peaks around green.
- jiehong 6y ago
  That power output really is the area under the curve, in which case most of the sun's energy is in the infrared, actually.
  - alanbernstein 6y ago
    Sure. But the peak is around green, which is the point of the article and the answer to parent's question.
deleted 6y ago
[deleted]
spacemark 6y ago
>First, green does not have the most energy of the visual spectrum, Blue, or more specific Violet does The article is correct. Blue photons have more energy, you're right. But more green photons are emitted by the sun, and even more reach the ground through the atmosphere than blue, so the total energy from green photons is significantly greater. Google blackbody spectrum. https://en.wikipedia.org/wiki/File:Wiens_law.svg https://en.wikipedia.org/wiki/File:Wiens_law.svg https://lh3.googleusercontent.com/proxy/eDhfILMl70XZ-WUchpgoEQn77K7dvrZZg2iY5F4vaXnHE85OCjrWZC3EHjvMRU6FmW9bNSZNHLvlKlO_uYfLJgO7DRO0iAzsTRBc https://lh3.googleusercontent.com/proxy/eDhfILMl70XZ-WUchpgo...

jonplackett 6y ago

I always just assumed there wasn't much green light, so plants optimised for the rest of the spectrum: The sky is blue, the sun is orangey. Where's all this green light I'm missing?

alanbernstein 6y ago
Look at a graph of the spectral power output of the sun, you'll see that it peaks around green.
sp332 6y ago
Your green receptors overlap with red, and also a little with blue. There is no single wavelength of light that only stimulates your green photoreceptors without also setting off red or blue ones. https://en.wikipedia.org/wiki/Color#/media/File:Cones_SMJ2_E.svg https://en.wikipedia.org/wiki/Color#/media/File:Cones_SMJ2_E...
colanderman 6y ago
The sun is actually green (that is, is approximated by a black body emitter with a peak in the green region of the visual spectrum, see [1]). Its light appears white because that is how we are conditioned evolutionarily. ("True" white -- i.e. equal spectral energy -- appears blue-grey to us.) The sun "looks" orange because when you can look at it (sunrise/sunset), its light is heavily filtered by the atmosphere. [1] https://qph.fs.quoracdn.net/main-qimg-f9bc312e4d114e9e32a62714c36580aa https://qph.fs.quoracdn.net/main-qimg-f9bc312e4d114e9e32a627...
projektfu 6y ago
Orange is red and green. The intensity we perceive is also not the absolute intensity of that part of the spectrum. Neither is the luminosity equivalent to the power (as in energy over time).

hawktheslayer 6y ago

I might just use this trick of nature to inform how I manage my staff at work. We spend so much time trying to maximize efficiently, but perhaps at the cost of stability.

deeweebee 6y ago
This is the nerdiest sentence I’ve seen today. Dang!

throwaway_USD 6y ago

My understanding of the evolution of Earth flora is that prior to plants being green, the dominant plant life was red (think of red algae blooms) and that the current dominant green plant life likely evolved to use different photons along the EM spectrum where there was less competition. Funny enough as I understand visible light and the EMR spectrum there is no "green" (color/wave length/energy) rather the color green is a construct originating not in the light spectrum but in the mind of the observer.

andrewflnr 6y ago
I was thinking about the same hypothesis but IIRC it was highly speculative, with the main evidence for it simply being that modern plants evolved to use those other photosynthesizers' castoffs. We may not need that hypothesis anymore if we have a solid reason to avoid green anyway.
Zaak 6y ago
There is a range of wavelengths of light that humans perceive as green. The same is true for every color that is part of the rainbow. In contrast, the "pure purples" do not appear in the rainbow, and there is no single wavelength of light that humans perceive as purple (it requires red light plus blue light).
- Balgair 6y ago
  The perception of color is a pretty wild area of science. Colors seem to be culturally dependent. In that, people literally cannot see the difference between blue and green if their language does not have words to distinguish them. Even when big rewards are given for the 'correct' answer. Colors also follow certain patterns, with colors like blue being the last to be named in a culture. https://www.youtube.com/watch?v=gMqZR3pqMjg https://www.youtube.com/watch?v=gMqZR3pqMjg Fun fact, the color blue does not appear at all in the Iliad, Homer describes the ocean as wine, despite the stunning blue colors of grecian seas.
  - sergeykish 6y ago

zadkey 6y ago

Why are some plants purple like tradescantia pallida?

Chris2048 6y ago

But, why do plants need a regular amount of light energy? Can't a black plant just absorb everything available?

odomojuli 6y ago

The color of plants and the statistics of light is fascinating. Tangentially related, I was developing a CV app for farmers in an early stage weed startup right before legalization in California so they could monitor analytics on the health of their sprouts as well as identify strains. The camera conditions were all over the place and data preprocessing stage was an absolute nightmare. We tried everything from filters to background removal, augmentation techniques through transformations, noise induction for generalization - nothing really improved the baseline models because the photos honestly sucked. Farmers ignored our guidelines on lighting and framing and format and kept sending in inconsistent garbage. I had a eureka moment. What if we sent each of the farmers a little piece of square cardboard painted magenta? The idea was that the increase in contrast would allow us to process the leaf contour a little bit better. The fact that the card was square meant some farmers even took the time to take the plant indoors so they could frame it better within the edges. Data quality improved dramatically. It worked. Unfortunately legalization did not work out as we planned, farmers disappeared and the market was monopolized by corporations, there wasn't any interest in helping develop strains locally.