"Retinal-containing cell membranes exhibit a single light absorption peak centered in the energy-rich green-yellow region of the visible spectrum, but transmit and reflect red and blue light, resulting in a magenta color.[5] Chlorophyll pigments, in contrast, absorb red and blue light, but little or no green light [..]"
I wonder why no plant evolved to use both and make the more even efficient use of light. These plats would appear dark, maybe almost black. They could live between all the green plants from their scraps so to speak.
"However, the porphyrin-based nature of chlorophyll had created an evolutionary trap[citation needed], dictating that chlorophyllic organisms cannot re-adapt to absorb the energy-rich and now-available green light, and therefore ended up reflecting and presenting a greenish color."
Scientific writing style is not always very good at highlighting the unknowns. "We don't know this" doesn't make very convincingly looking text, so people tend to avoid admitting it up front.
But you are, of course, correct to ask.
Like another comments said, this is an open question.
One theory is, that while the algae floating in water were absorbing broad spectrum, the algae growing attached at the bottom of the water evolved to chlorophyll to capture whatever was left at the edges of the spectrum. And then later land-based plants would have evolved from the water plants that were already attaching themselves to the bottom. But then why are also the current ocean-floating algae green now?
Another theory is that a perfectly-absorbing leaf would somehow absorb too much energy and get overheated, and that it was better to absorb only part of the available light.
None of these theories are fully convincing, so the question remains open.
According to the article, at least todays retinal-based photosynthesis is anoxygenic and does not invole carbon fixation. At night, these cells metabolism stops. Chlorophyllic photosynthesis with attached carbon fixation allows the cell to build up starch during the day, which it breathes under the use of oxygen at night, so the cell remains active during the night. Looks like a big evolutionary advantage to me.
Also, light is not the limiting factor for plant growth, it‘s usually water or nutrient availability.
carbon fixation is a completely separate process. in principle you could hook up a sufficiently engineered cell to electrodes and do the carbon fixation part in the dark by supplying it with juice from the mains.
accordingly there is no particular reason for purple photon assimilation to not be attached to carbon fixation... though i suppose as the electron energy levels dont quite match up it might be a schlep to get purples to make sugar.
> "We don't know this" doesn't make very convincingly looking text, so people tend to avoid admitting it up front.
Saying definitively that we don't know something (1) requires an investment of time to verify that lack of knowledge, and (2) can become incorrect at any time.
If you want to do something with the answer but find that it doesn't exist, sure make a note of that to request that someone could maybe try to find out. But if it's just a curiosity rather than directly relevant, why bother?
> Saying definitively that we don't know something (1) requires an investment of time to verify that lack of knowledge, and (2) can become incorrect at any time.
And (3) doesn’t necessarily make you lose credibility but too many believe it does and partially it can.
Those who believe science is truth are innocently choosing an answer without full knowledge. That is the definition of religion and faith.
True science is a search for truth like philosophy and theology. I think you can get too caught up in any one of these three.
If you have hard core faith, that’s awesome, but put your faith into that which won’t fail you.
In science, there is clear delineation between things we know to be true (laws), things that appear to be true based on our current knowledge (theories) and things that may or may not be true but seem to be true based on limited data/limited research (hypotheses).
I don't think the three (I only see two, though, but don't want to nitpick) approaches are really comparable.
Newton's First Law (Law of Inertia) – assumes objects remain at rest or in uniform motion unless acted upon by an external force; inaccurate in non-inertial (accelerating) frames without fictitious forces.
Newton's Second Law – assumes constant mass and low velocities; inaccurate at relativistic speeds where mass increases with velocity.
Newton's Third Law – inaccurate in electromagnetic, quantum, or relativistic contexts.
Newton's Law of Universal Gravitation – assumes instantaneous action at a distance and weak fields; replaced by General Relativity in strong fields or at high velocities.
Boyle's Law – inaccurate at high pressures, low temperatures, or with real gases, which deviate from ideal behavior.
Charles's Law – assumes ideal gas behavior; deviations occur at high pressures or low temperatures.
Ohm's Law – assumes constant resistance; inaccurate for non-ohmic materials like diodes or at high voltages where resistance varies.
2nd Law of Thermodynamics – inaccurate with fluctuations at microscopic scales, temporarily decreasing entropy.
Kepler's Laws – inaccurate when considering relativistic effects.
Laws of Motion of Fluids (e.g., Bernoulli's Law) – assumes incompressible, non-viscous flow; inaccurate for real fluids with viscosity or compressibility effects.
Dalton's Law of Partial Pressures – assumes gases do not interact; inaccurate at high pressures or with strong intermolecular forces.
Fick's Laws of Diffusion - inaccurate in complex systems with reactions or non-constant diffusion coefficients.
Laws of Electromagnetic Induction (Faraday's Law) – assumes ideal conditions; real systems have hysteresis and other non-ideal effects.
Laws of Radioactive Decay – exponential decay is inaccurate as does not fully regard environment or decay chain complexities.
Fair enough. At which point do these non applicabilities make you think that the fact of putting your faith in science is bad? I mean, I tried to point out that science is a process, and yes, laws come with caveats. Some of them are known in advance, some not.
The search for truth, if we are still arguing that, where is it? I don't understand how anybody can argue that the search is the same across theology and science. In a sense it is the search for the same thing, but in so many ways it is not. The commenter I was replying to is confounding the difference, and this comment, seems to ask me to point out what mistakes theology made, and I know of plenty.
Principle seems to be the modern equivalent term to the concept that used to be represented by the word "law," in this context. I've also seen them used interchangeably on various things: "principle of least action" vs "law of least action" is a pretty common example.
How about this: it takes energy to build a photo-synthesis machine. A machine like this won't consume all photons but only some range of electromagnetic spectrum. This is because you need to have such structure to allow light to pass through the outer part of the body of the organism, but be absorbed at a very specific place inside. This is why multi-junction solar cells exist, to use more of the solar spectrum. It would cost a plant more energy to build such a multi-layered chloroplast, so perhaps having just a single layer using a single range of the spectrum is the most optimal (at least as a local maximum).
> Another theory is that a perfectly-absorbing leaf would somehow absorb too much energy and get overheated
If having both pigments means the plant would be close to black, overheating is an absolutely valid hypothesis imo, plants just like animals have optimal temperature metabolism and often getting too hot is deadly, while under optimal temperature is tolerable.
sure but there are probably ecological niches that are light starved. for instance deeper in the water column or in dark areas like caves or polar regions
Evolution is only possible along certain paths, for example, we are not going to evolve to have more than four limbs, eyes at the back of our heads or extra hands.
Similarly, at the cell level, we have just the one photosynthesis process in plants and that isn't going to take an entirely different path to work on different wavelengths. The evolutionary investment is in chlorophyll with a magnesium element at the heart of it. Imaginably you would need an entirety different molecule with some other magic atom in the middles of the usual organic chemistry and that isn't going to happen given the sunk cost in the chlorophyll way of doing things. There is a greater chance that we will get six hands than that happening.
Indeed, and frequently you will see that leaves are a much darker hue of green than the ones exposed directly to sunlight. So, using the same mechanism, still more is absorbed if light is scarce.
Of course, for example several sea weeds come to mind in dark green to brown tones; which makes sense, they can disperse heat very fast since they are immersed in cold water / liquid cooling
- Terrestrial plants evolved from green algae. There are other colors of photosynthetic algae. The advantage of absorbing red and blue may have been about avoiding competition with nearby red algae (which absorbs green), and about how blue light penetrates more deeply.
- The trick is not capturing as much energy as possible, but rather capturing and routing energy to the reaction centers such that it neither overshoots nor undershoots the energy necessary for the reaction. This works better with two absorption peaks instead of one (more here: https://www.quantamagazine.org/why-are-plants-green-to-reduc...). The absorption peaks of chlorophyll are both adequately distant from one another, and also more or less centered on the visible (i.e. most energetic) spectrum emitted by the sun.
I agree with the overall discussion, but in the last link (Curtis Mobley Ocean Optics Book) the argument is broken.
Mobley plotted two graphs of the solar irradiation and a black body fit. The only difference is supposed to be the x axis with a plot over frequency or wavelength. This is a non-linear mapping and a different shape is expected. But the result is that the peak irradiation level is at either 501nm or 882nm (when converted back). That can't be right. The labeling of the x axis does not change the maximum.
What he meant to do was to plot either the solar irradiation in W m^-2 nm^-1 or as the number of photons. With lower energy photons (towards the red) the same irradiation level will consist of more photons. This shifts the maximum number of photons towards higher wavelengths. 880nm sounds plausible.
While all the phototrophs that are able to split water and produce free oxygen use chlorophyll a, which absorbs only red light and violet light, resulting in a blue-green color, which can be seen as such in some lichens and cyanobacteria, most of them have some accessory pigments, which absorb other parts of the solar spectrum, and then transfer the energy to chlorophyll a.
The green algae, which live only in shallow waters, and the terrestrial plants use as accessory pigment only chlorophyll b, which absorbs a different band of red light than chlorophyll a and also blue light, resulting in a green color.
This is enough for green algae and land plants, because where they live there is abundant light. For land plants the problem is that they have too much light, not too little, with the exception of those which grow under the shadow of trees.
On the other hand, most marine algae use accessory pigments that absorb much more of the solar spectrum, so that the color of chlorophyll is no longer visible and they have overall colors like red, yellow or brown, even very dark brown. This enables such algae to live down to greater depths in the water, where there is less solar light.
So there are a lot of living beings that make very efficient use of light.
Moreover, under water there are many places where practically all light is captured, by multiple layers of algae and bacteria, each layer absorbing some part of the solar spectrum. Even the near infrared light is absorbed by a bottom layer of bacteria, which do not produce oxygen, because the energy of infrared photons is insufficient to split water.
technically the energy in green is also not enough to split water, which (IIRC) is why PSII must ping pong the photon through multiple collector complexes to achieve an electron with enough energy to crack water.
The energy required to split water is around 1.25 eV, while the energy of red photons is already around 1.5 V and the energy of green photons is well above 2 eV.
However, it is true that plants need 2 red photons (or of higher energy), not 1, to generate both free oxygen and a reduced organic substance, NADPH, which is used later to reduce carbon dioxide into carbohydrates. The reason is that the captured solar energy is used not only for these redox reactions, but also for pumping ions across the chloroplast membrane. The energy stored in the ion gradient will be used later to power the chemical syntheses, which need both a reducing agent and additional energy.
The ping-pong is done with electrons, not with photons. There are 2 photosystems, which absorb separately photons, using their energy to transport electrons against the potential gradient. The electrons pass through both photosystems in series, achieving a potential difference between the endpoints that is greater than what is required for splitting water.
The potential difference over each photosystem is significantly smaller than corresponding to the energy of the absorbed photon, because only a fraction of the energy is used for electron transport against a potential gradient, while the rest is used for ion transport against a ion concentration gradient.
Photosystem II contains manganese ions that are oxidized so strongly that they can oxidize the oxygen from water, converting it into free dioxygen. Photosystem I is able to make a strong reducing agent, to which the hydrogen remaining from water is bound.
As far as I understand it, this is a still debated question. One theory is it's about evaporating water: Plausible photomolecular effect leading to water evaporation exceeding the thermal limit (https://www.pnas.org/doi/10.1073/pnas.2312751120).
There are black plants though! And they're studied for the same kind of questions. E.g. The Functional Significance of Black-Pigmented Leaves: Photosynthesis, Photoprotection and Productivity in Ophiopogon planiscapus ‘Nigrescens’ (https://pmc.ncbi.nlm.nih.gov/articles/PMC3691134/)
A few different threads based on my limited online research:
1. Absorbing all spectrum of light would provide more energy than the organisms can handle. They need gas to run the engine, and all spectrum would provide jet fuel.
2. Current predominant species of plants evolved from the undergrowth. Original plants would absorb only green, so the undergrowth evolved to absorb the other spectrums because that’s what was left. After a few planet scale extinction events where the sunlight was scarce, being able to absorb a wider spectrum became a successful evolutionary trait and became the predominant one.
3. There are species of fungi that use melanin to absorb radiation for energy source and appear black.
> Absorbing all spectrum of light would provide more energy than the organisms can handle. They need gas to run the engine, and all spectrum would provide jet fuel.
one could ask why not a bigger/powerful organism. and a nice answer for that would be: more energy, more stuff going on, more bad mutations having the chance to exist; impaired evolution ;)
Most of the green reflectance is an illusion because the human retina amplifies green light as much as 25× more than red (think of a green 5mw laser vs red).
This is actually even more puzzling than it seems, because the green part of the spectrum is the most energetic.
I've read elsewhere that photosynthesis is partially limited by dealing with free radicals, and at peak light flux, many plants would be damaged by the monoatomic oxygen species that light-capturing complexes would create. Hence pigments that reflect some green light.
I see that as a positive, not a negative. Since the pellets can be sold, investors are more likely to invest in the development of the process. And the extra volume of production tends to increase the efficiency, i.e., to reduce the cost (paid by altruists and governments) of producing the pellets that do end up in the ground or in ocean trenches.
Evolution simply describes the macro process of death and birth as affected by the environment, no improvement planned. It could well be that a certain set of traits survive purely by chance or slightly improved odds in one set of circumstances that are detrimental later.
> I wonder why no plant evolved to use both and make the more even efficient use of light. These plats would appear dark, maybe almost black.
Many varieties of seaweed would seem to meet the description. Although I'm not sure that any of them are naturally anything like black without processing. Certainly some of them are brown, though.
IIRC, PSI in the photosynthetic complex comes from purple bacteria, and PSII from green sulfur bacteria, so cyanos (and thus chloroplasts) kind of "already are" "using both". one presumes the option to use both pigments in the harvesting sense has been sampled evolutionarily.
no, that doesn't make sense because the cells are being irradiated at those wavelengths anyways. Absorption in uv would if anything, shade the cell from uv induced damage.
Fun fact, early hand written lyrics were "purple haze, Jesus saves...". It was a recollection of a dream where he was walking under water. The connection to acid is more so by interpretation of the audience.
Less accessible. Illicit LSD production will probably never be as widespread as it was before the List of Chemicals was introduced. You can develop alternative manufacturing methods for most drugs. But a hexahydroindolo[4,3-fg]quinoline? Not so easy.
> LSD became less popular in the underground drug culture.
Hmmmm...
Maybe relatively less popular, as the menu of recreational drugs is expanded from a very few bad ones to a cornucopia of good ones, but still very popular
LSD definitely had a resurgence and it's very popular again today, but it's still accurate to say it lost popularity the crackdowns at the end of the 60s.
Problem was in the 90s most North American supply was apparently coming from a couple of guys and when they got busted it almost disappeared overnight.
Yeah there was the mini resurgence in the late 80s, early 90s but I think the scene since the start of the 2010s has grown to be bigger than ever in a certain sense.
We really don't give enough credit to the people that maintain Wikipedia and do the work required to make these articles. Its a shame that a lot of political / social influence has started to creep into some of the articles but on the whole its really an incredible benefit to humanity.
Considering assembly theory (https://en.m.wikipedia.org/wiki/Assembly_theory) for a possible explanation. The OP does state retinal is simpler, but it's significantly more basic and is organic.
On the other hand: Chlorophyll(s) all have a single magnesium caught at the center of a chlorin 'net'. It seems significantly harder to manufacture!
Do you think it is just coincidence that chlorophyll is green and sun has peak luminosity in green frequencies? Or did chlorophyll win just because of that?
In the rest of the niches in the entire domain of life it is the case that many different strategies were tried simultaneously, usually with a sole predominating outcome.
Something similar happened with me for another theory's article. I knew it existed before the article said. But I only had a primary source to prove it. Since it's not a secondary source I couldn't fix the article, so I put it on the talk page. Now the talk page has been wiped and the article is still wrong about the origin.
Happens frequently. Usually the Wikipedia article is written by the guy who wants to claim credit for an existing design or idea, so he zealously guards the page against the truth. It's just disappointing.
No that's just a pigment. They still contain chlorophyll.
Often you'll find leaves in full sun are redder, because they need less chlorophyll to operate at full efficiency. Leaves more in shade may be darker, as they require more chlorophyll (meaning light is absorbed across most of the visual spectrum by the pigment and chlorophyll together)
"Retinal-containing cell membranes exhibit a single light absorption peak centered in the energy-rich green-yellow region of the visible spectrum, but transmit and reflect red and blue light, resulting in a magenta color.[5] Chlorophyll pigments, in contrast, absorb red and blue light, but little or no green light [..]"
I wonder why no plant evolved to use both and make the more even efficient use of light. These plats would appear dark, maybe almost black. They could live between all the green plants from their scraps so to speak.
"However, the porphyrin-based nature of chlorophyll had created an evolutionary trap[citation needed], dictating that chlorophyllic organisms cannot re-adapt to absorb the energy-rich and now-available green light, and therefore ended up reflecting and presenting a greenish color."
Yes, but why?
> Yes, but why?
Scientific writing style is not always very good at highlighting the unknowns. "We don't know this" doesn't make very convincingly looking text, so people tend to avoid admitting it up front.
But you are, of course, correct to ask.
Like another comments said, this is an open question.
One theory is, that while the algae floating in water were absorbing broad spectrum, the algae growing attached at the bottom of the water evolved to chlorophyll to capture whatever was left at the edges of the spectrum. And then later land-based plants would have evolved from the water plants that were already attaching themselves to the bottom. But then why are also the current ocean-floating algae green now?
http://hyperphysics.phy-astr.gsu.edu/hbase/Biology/imgbio/pl...
Another theory is that a perfectly-absorbing leaf would somehow absorb too much energy and get overheated, and that it was better to absorb only part of the available light.
None of these theories are fully convincing, so the question remains open.
According to the article, at least todays retinal-based photosynthesis is anoxygenic and does not invole carbon fixation. At night, these cells metabolism stops. Chlorophyllic photosynthesis with attached carbon fixation allows the cell to build up starch during the day, which it breathes under the use of oxygen at night, so the cell remains active during the night. Looks like a big evolutionary advantage to me. Also, light is not the limiting factor for plant growth, it‘s usually water or nutrient availability.
carbon fixation is a completely separate process. in principle you could hook up a sufficiently engineered cell to electrodes and do the carbon fixation part in the dark by supplying it with juice from the mains.
accordingly there is no particular reason for purple photon assimilation to not be attached to carbon fixation... though i suppose as the electron energy levels dont quite match up it might be a schlep to get purples to make sugar.
> "We don't know this" doesn't make very convincingly looking text, so people tend to avoid admitting it up front.
Saying definitively that we don't know something (1) requires an investment of time to verify that lack of knowledge, and (2) can become incorrect at any time.
If you want to do something with the answer but find that it doesn't exist, sure make a note of that to request that someone could maybe try to find out. But if it's just a curiosity rather than directly relevant, why bother?
> Saying definitively that we don't know something (1) requires an investment of time to verify that lack of knowledge, and (2) can become incorrect at any time.
And (3) doesn’t necessarily make you lose credibility but too many believe it does and partially it can.
Those who believe science is truth are innocently choosing an answer without full knowledge. That is the definition of religion and faith.
True science is a search for truth like philosophy and theology. I think you can get too caught up in any one of these three.
If you have hard core faith, that’s awesome, but put your faith into that which won’t fail you.
I am sorry but I don't quite agree with you.
In science, there is clear delineation between things we know to be true (laws), things that appear to be true based on our current knowledge (theories) and things that may or may not be true but seem to be true based on limited data/limited research (hypotheses).
I don't think the three (I only see two, though, but don't want to nitpick) approaches are really comparable.
Scientific laws are not solid.
Newton's First Law (Law of Inertia) – assumes objects remain at rest or in uniform motion unless acted upon by an external force; inaccurate in non-inertial (accelerating) frames without fictitious forces.
Newton's Second Law – assumes constant mass and low velocities; inaccurate at relativistic speeds where mass increases with velocity.
Newton's Third Law – inaccurate in electromagnetic, quantum, or relativistic contexts.
Newton's Law of Universal Gravitation – assumes instantaneous action at a distance and weak fields; replaced by General Relativity in strong fields or at high velocities.
Boyle's Law – inaccurate at high pressures, low temperatures, or with real gases, which deviate from ideal behavior.
Charles's Law – assumes ideal gas behavior; deviations occur at high pressures or low temperatures.
Ohm's Law – assumes constant resistance; inaccurate for non-ohmic materials like diodes or at high voltages where resistance varies.
2nd Law of Thermodynamics – inaccurate with fluctuations at microscopic scales, temporarily decreasing entropy.
Kepler's Laws – inaccurate when considering relativistic effects.
Laws of Motion of Fluids (e.g., Bernoulli's Law) – assumes incompressible, non-viscous flow; inaccurate for real fluids with viscosity or compressibility effects.
Dalton's Law of Partial Pressures – assumes gases do not interact; inaccurate at high pressures or with strong intermolecular forces.
Fick's Laws of Diffusion - inaccurate in complex systems with reactions or non-constant diffusion coefficients.
Laws of Electromagnetic Induction (Faraday's Law) – assumes ideal conditions; real systems have hysteresis and other non-ideal effects.
Laws of Radioactive Decay – exponential decay is inaccurate as does not fully regard environment or decay chain complexities.
Fair enough. At which point do these non applicabilities make you think that the fact of putting your faith in science is bad? I mean, I tried to point out that science is a process, and yes, laws come with caveats. Some of them are known in advance, some not.
The search for truth, if we are still arguing that, where is it? I don't understand how anybody can argue that the search is the same across theology and science. In a sense it is the search for the same thing, but in so many ways it is not. The commenter I was replying to is confounding the difference, and this comment, seems to ask me to point out what mistakes theology made, and I know of plenty.
So that’s why there are no new laws these days?
Principle seems to be the modern equivalent term to the concept that used to be represented by the word "law," in this context. I've also seen them used interchangeably on various things: "principle of least action" vs "law of least action" is a pretty common example.
It is common for authors to say that "We are not aware an explanation as of now."
How about this: it takes energy to build a photo-synthesis machine. A machine like this won't consume all photons but only some range of electromagnetic spectrum. This is because you need to have such structure to allow light to pass through the outer part of the body of the organism, but be absorbed at a very specific place inside. This is why multi-junction solar cells exist, to use more of the solar spectrum. It would cost a plant more energy to build such a multi-layered chloroplast, so perhaps having just a single layer using a single range of the spectrum is the most optimal (at least as a local maximum).
> Another theory is that a perfectly-absorbing leaf would somehow absorb too much energy and get overheated
If having both pigments means the plant would be close to black, overheating is an absolutely valid hypothesis imo, plants just like animals have optimal temperature metabolism and often getting too hot is deadly, while under optimal temperature is tolerable.
sure but there are probably ecological niches that are light starved. for instance deeper in the water column or in dark areas like caves or polar regions
Evolution is only possible along certain paths, for example, we are not going to evolve to have more than four limbs, eyes at the back of our heads or extra hands.
Similarly, at the cell level, we have just the one photosynthesis process in plants and that isn't going to take an entirely different path to work on different wavelengths. The evolutionary investment is in chlorophyll with a magnesium element at the heart of it. Imaginably you would need an entirety different molecule with some other magic atom in the middles of the usual organic chemistry and that isn't going to happen given the sunk cost in the chlorophyll way of doing things. There is a greater chance that we will get six hands than that happening.
Indeed, and frequently you will see that leaves are a much darker hue of green than the ones exposed directly to sunlight. So, using the same mechanism, still more is absorbed if light is scarce.
Of course, for example several sea weeds come to mind in dark green to brown tones; which makes sense, they can disperse heat very fast since they are immersed in cold water / liquid cooling
I asked this same question last week and got some good answers: https://news.ycombinator.com/item?id=44630224
Three things that stood out to me:
- Terrestrial plants evolved from green algae. There are other colors of photosynthetic algae. The advantage of absorbing red and blue may have been about avoiding competition with nearby red algae (which absorbs green), and about how blue light penetrates more deeply.
- The trick is not capturing as much energy as possible, but rather capturing and routing energy to the reaction centers such that it neither overshoots nor undershoots the energy necessary for the reaction. This works better with two absorption peaks instead of one (more here: https://www.quantamagazine.org/why-are-plants-green-to-reduc...). The absorption peaks of chlorophyll are both adequately distant from one another, and also more or less centered on the visible (i.e. most energetic) spectrum emitted by the sun.
- The idea that the green-yellow region of the visible spectrum is most energetic is, if not a misconception, at least more complex that it seems (https://www.oceanopticsbook.info/view/light-and-radiometry/l...).
I agree with the overall discussion, but in the last link (Curtis Mobley Ocean Optics Book) the argument is broken.
Mobley plotted two graphs of the solar irradiation and a black body fit. The only difference is supposed to be the x axis with a plot over frequency or wavelength. This is a non-linear mapping and a different shape is expected. But the result is that the peak irradiation level is at either 501nm or 882nm (when converted back). That can't be right. The labeling of the x axis does not change the maximum.
What he meant to do was to plot either the solar irradiation in W m^-2 nm^-1 or as the number of photons. With lower energy photons (towards the red) the same irradiation level will consist of more photons. This shifts the maximum number of photons towards higher wavelengths. 880nm sounds plausible.
No, see previous discussion here: https://news.ycombinator.com/item?id=44632819
While all the phototrophs that are able to split water and produce free oxygen use chlorophyll a, which absorbs only red light and violet light, resulting in a blue-green color, which can be seen as such in some lichens and cyanobacteria, most of them have some accessory pigments, which absorb other parts of the solar spectrum, and then transfer the energy to chlorophyll a.
The green algae, which live only in shallow waters, and the terrestrial plants use as accessory pigment only chlorophyll b, which absorbs a different band of red light than chlorophyll a and also blue light, resulting in a green color.
This is enough for green algae and land plants, because where they live there is abundant light. For land plants the problem is that they have too much light, not too little, with the exception of those which grow under the shadow of trees.
On the other hand, most marine algae use accessory pigments that absorb much more of the solar spectrum, so that the color of chlorophyll is no longer visible and they have overall colors like red, yellow or brown, even very dark brown. This enables such algae to live down to greater depths in the water, where there is less solar light.
So there are a lot of living beings that make very efficient use of light.
Moreover, under water there are many places where practically all light is captured, by multiple layers of algae and bacteria, each layer absorbing some part of the solar spectrum. Even the near infrared light is absorbed by a bottom layer of bacteria, which do not produce oxygen, because the energy of infrared photons is insufficient to split water.
technically the energy in green is also not enough to split water, which (IIRC) is why PSII must ping pong the photon through multiple collector complexes to achieve an electron with enough energy to crack water.
Nope.
The energy required to split water is around 1.25 eV, while the energy of red photons is already around 1.5 V and the energy of green photons is well above 2 eV.
However, it is true that plants need 2 red photons (or of higher energy), not 1, to generate both free oxygen and a reduced organic substance, NADPH, which is used later to reduce carbon dioxide into carbohydrates. The reason is that the captured solar energy is used not only for these redox reactions, but also for pumping ions across the chloroplast membrane. The energy stored in the ion gradient will be used later to power the chemical syntheses, which need both a reducing agent and additional energy.
The ping-pong is done with electrons, not with photons. There are 2 photosystems, which absorb separately photons, using their energy to transport electrons against the potential gradient. The electrons pass through both photosystems in series, achieving a potential difference between the endpoints that is greater than what is required for splitting water.
The potential difference over each photosystem is significantly smaller than corresponding to the energy of the absorbed photon, because only a fraction of the energy is used for electron transport against a potential gradient, while the rest is used for ion transport against a ion concentration gradient.
Photosystem II contains manganese ions that are oxidized so strongly that they can oxidize the oxygen from water, converting it into free dioxygen. Photosystem I is able to make a strong reducing agent, to which the hydrogen remaining from water is bound.
As far as I understand it, this is a still debated question. One theory is it's about evaporating water: Plausible photomolecular effect leading to water evaporation exceeding the thermal limit (https://www.pnas.org/doi/10.1073/pnas.2312751120).
There are black plants though! And they're studied for the same kind of questions. E.g. The Functional Significance of Black-Pigmented Leaves: Photosynthesis, Photoprotection and Productivity in Ophiopogon planiscapus ‘Nigrescens’ (https://pmc.ncbi.nlm.nih.gov/articles/PMC3691134/)
Nigrescens is overdue a 'naming review' with the Culture Ministry.
A few different threads based on my limited online research:
1. Absorbing all spectrum of light would provide more energy than the organisms can handle. They need gas to run the engine, and all spectrum would provide jet fuel.
2. Current predominant species of plants evolved from the undergrowth. Original plants would absorb only green, so the undergrowth evolved to absorb the other spectrums because that’s what was left. After a few planet scale extinction events where the sunlight was scarce, being able to absorb a wider spectrum became a successful evolutionary trait and became the predominant one.
3. There are species of fungi that use melanin to absorb radiation for energy source and appear black.
> Absorbing all spectrum of light would provide more energy than the organisms can handle. They need gas to run the engine, and all spectrum would provide jet fuel.
one could ask why not a bigger/powerful organism. and a nice answer for that would be: more energy, more stuff going on, more bad mutations having the chance to exist; impaired evolution ;)
In fact, many plants already receive too much sunlight and have various mechanisms to limit their exposure.
Most of the green reflectance is an illusion because the human retina amplifies green light as much as 25× more than red (think of a green 5mw laser vs red).
On the other hand, leaves do absorb green light: nearly 75% is absorbed, in contrast to 85% of non-green light. See https://www.researchgate.net/figure/Reflectance-spectra-of-g...
Would osmin basil[1] fit the bill?
[1] https://www.google.com/search?client=safari&sa=X&sca_esv=923...
This is actually even more puzzling than it seems, because the green part of the spectrum is the most energetic.
I've read elsewhere that photosynthesis is partially limited by dealing with free radicals, and at peak light flux, many plants would be damaged by the monoatomic oxygen species that light-capturing complexes would create. Hence pigments that reflect some green light.
Article:
https://www.quantamagazine.org/why-are-plants-green-to-reduc...
Evolution has had billions of years to improve on photosynthesis, but there still seems to be a lot left in the table.
Could we engineer a more efficient photosynthesis?
> Could we engineer a more efficient photosynthesis?
Yes! They’re called solar panels, and our best ones are about 4x more efficient than the most efficient photosynthesis processes in nature, afaik.
A tree grows a leaf slightly more efficiently than we create a solar panel though.
Solar panels so far don't remove CO2 from the air, though.
You can connect them with other equipment to do that, if that’s your goal. Not very effective though
The removal is only temporary.
Can be a couple of hundred years with trees and wood used for housing. Long enough to figure things out
Not if the panels were to produce graphite pellets that people could bury or dump in ocean trenches.
We both know people would burn graphite pellets. That’s what we do with wood pellets today.
I see that as a positive, not a negative. Since the pellets can be sold, investors are more likely to invest in the development of the process. And the extra volume of production tends to increase the efficiency, i.e., to reduce the cost (paid by altruists and governments) of producing the pellets that do end up in the ground or in ocean trenches.
It might actually help with financing the things. I guess it is almost carbon neutral. Zero efficient though.
That’s what I’m using as the benchmark, but I was thinking more like bio engineering to create an organism that gets closer to solar panel efficiency.
Would be potentially very useful for timber or biomass production. I doubt people would trust eating it.
> Evolution ... improve[d] on photosynthesis
Evolution simply describes the macro process of death and birth as affected by the environment, no improvement planned. It could well be that a certain set of traits survive purely by chance or slightly improved odds in one set of circumstances that are detrimental later.
> I wonder why no plant evolved to use both and make the more even efficient use of light. These plats would appear dark, maybe almost black.
Many varieties of seaweed would seem to meet the description. Although I'm not sure that any of them are naturally anything like black without processing. Certainly some of them are brown, though.
Brown kelp uses fucoxanthin to absorb green light. But they’re no longer considered to be plants.
IIRC, PSI in the photosynthetic complex comes from purple bacteria, and PSII from green sulfur bacteria, so cyanos (and thus chloroplasts) kind of "already are" "using both". one presumes the option to use both pigments in the harvesting sense has been sampled evolutionarily.
oops i got them backwards, psII comes from purple.
> I wonder why no plant evolved to use both and make the more even efficient use of light. These plats would appear dark, maybe almost black.
I have seen some black plants around where I live.
Doesn't mean they're photosynthesising with all frequencies of light though. Probably just pigment.
It might be better to be exclude IR and UV so they don’t have to spend a lot of resources on cooling and anti mutagenic devices.
no, that doesn't make sense because the cells are being irradiated at those wavelengths anyways. Absorption in uv would if anything, shade the cell from uv induced damage.
I think that retinal might react with porphyrins. The former is a reactive aldehyde, the latter is a pyrrole derivative.
PBS Eons has an episode on this:
When the Earth Was Purple https://m.youtube.com/watch?v=IIA-k_bBcL0
(This is great science channel. PBS should have continued to receive federal funding.)
Jimi was right—Earth was in a purple haze. It just came from retinal-based photosynthesizers, not acid.
Fun fact, early hand written lyrics were "purple haze, Jesus saves...". It was a recollection of a dream where he was walking under water. The connection to acid is more so by interpretation of the audience.
It's not more associated to cannabis? There's many strains even named for it.
This presumably happened later, as LSD became less popular in the underground drug culture.
Less accessible. Illicit LSD production will probably never be as widespread as it was before the List of Chemicals was introduced. You can develop alternative manufacturing methods for most drugs. But a hexahydroindolo[4,3-fg]quinoline? Not so easy.
> LSD became less popular in the underground drug culture.
Hmmmm...
Maybe relatively less popular, as the menu of recreational drugs is expanded from a very few bad ones to a cornucopia of good ones, but still very popular
LSD definitely had a resurgence and it's very popular again today, but it's still accurate to say it lost popularity the crackdowns at the end of the 60s.
Problem was in the 90s most North American supply was apparently coming from a couple of guys and when they got busted it almost disappeared overnight.
Yeah there was the mini resurgence in the late 80s, early 90s but I think the scene since the start of the 2010s has grown to be bigger than ever in a certain sense.
Nowadays I only ever hear people talk about it in the context of former users, or general discussion of the 70s.
We really don't give enough credit to the people that maintain Wikipedia and do the work required to make these articles. Its a shame that a lot of political / social influence has started to creep into some of the articles but on the whole its really an incredible benefit to humanity.
Considering assembly theory (https://en.m.wikipedia.org/wiki/Assembly_theory) for a possible explanation. The OP does state retinal is simpler, but it's significantly more basic and is organic.
On the other hand: Chlorophyll(s) all have a single magnesium caught at the center of a chlorin 'net'. It seems significantly harder to manufacture!
Do you think it is just coincidence that chlorophyll is green and sun has peak luminosity in green frequencies? Or did chlorophyll win just because of that?
Chlorophyll reflects green light, meaning it doesn't use these frequencies.
Who knows, maybe that's why the retinal photosynthesis evolved first though.
Maybe other frequencies “taste” better.
And that’s why many humans don’t like eating their greens, because even plants don’t like greens.
In the rest of the niches in the entire domain of life it is the case that many different strategies were tried simultaneously, usually with a sole predominating outcome.
This page says the theory was first proposed in 2007, but I remember being told about it at university around 2003.
Something similar happened with me for another theory's article. I knew it existed before the article said. But I only had a primary source to prove it. Since it's not a secondary source I couldn't fix the article, so I put it on the talk page. Now the talk page has been wiped and the article is still wrong about the origin.
Happens frequently. Usually the Wikipedia article is written by the guy who wants to claim credit for an existing design or idea, so he zealously guards the page against the truth. It's just disappointing.
I remember vaguely reading about this in the 1970s, maybe Scientific American? Cannot find that article now though.
Is this seen in some trees today?
Near me there is a plum tree with purple leaves
Not mentioned in the article...
No that's just a pigment. They still contain chlorophyll.
Often you'll find leaves in full sun are redder, because they need less chlorophyll to operate at full efficiency. Leaves more in shade may be darker, as they require more chlorophyll (meaning light is absorbed across most of the visual spectrum by the pigment and chlorophyll together)
Someone should add citations to the Evidence section.
So the world might've been purple in the past...
That's really neat!