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Why are plants green? To reduce the noise in photosynthesis
- Yaa101 4y agoInteresting, apart from more efficient solar panels it could hand us a solution to better protect our skins with colored sunblock.
- greenthrow 4y agoSolar panels are already much, much more efficient than photosynthesis.
- _alxk 4y agoThat doesn't preclude that further optimisation of solar panels could stem from research on photosynthesis.
- akira2501 4y agoPerhaps.. but part of the reason plants "lack efficiency" compared to our solid state electronics is that they need respiration to exchange input and output products with the environment and the entire plant needs to be laid out in such a way that it can maintain a root structure while being advantaged with respect to competing vegetation. The two problem spaces are similar in that they use light, but exceptionally different in almost every other respect.
- lazide 4y agoAlso, sunburn is a real problem (aka excessive sun) without enough water or other nutrients for them.
- delecti 4y agoI'm not sure the same consideration applies to sunblock. The article makes the case that plants always "want" to let through the same quantity of light, but not necessarily the same proportion, while we ideally want to block 100% of UV all the time.
- dieselerator 4y agoI think this might be a good place to add this reminder: "Vitamin D is made when UV (more precisely, UVB rays) react with a compound (7-dehydrocholesterol) in the skin. The best rays for UV synthesis have wavelengths between 270–300 nm." [1] [1] https://www.sciencelearn.org.nz/resources/1313-vitamin-d-and-uv https://www.sciencelearn.org.nz/resources/1313-vitamin-d-and...
- lightedman 4y ago270nm is UVC territory. Did you mean 280nm instead?
- dieselerator 4y agoThat is a fair question. This is what I find. [1] Ultraviolet B UV‑B 280–315 Ultraviolet C UV‑C 100–280 [1] https://en.wikipedia.org/wiki/Ultraviolet https://en.wikipedia.org/wiki/Ultraviolet My read is "UVB" is the popular medicine way of saying UV is needed for the body to synthesize vitamin D. It was not considered necessary to point out part of the useful spectrum is in "UVC" territory.
- hinkley 4y agoAlso kills microbes on surfaces.
- OhNoNotAnother1 4y ago
- dvh 4y agoBecause sun is green.
- VierScar 4y agoSun white
- kzrdude 4y agoAfter passing through the atmosphere, the sunlight is strongest in the green (of the visible spectrum).
- deleted 4y ago[deleted]
- wyager 4y agoThe sun barely looks different from an artificial blackbody of the same temperature. The atmosphere is not a big consideration here.
- kzrdude 4y agoAha. When looking at a spectrum recorded through the atmosphere, that's how it has to be reported (so that's my thinking, why I would say it like that).
- cdumler 4y agoThe sun is classed as a green star[1]. As a black-body object, it emits the most light in the green spectrum. We see white because we evolved to distinguish color based on our star; however, our ability to detect variance in brightness in colors is far more limited. We, in fact, use this to our advantage. View screens transmit exactly brightness in narrow red, green, and blue such to fool our eyes into believing we see colors there that are not in fact there, such as red and green light to simulate yellow light. [1] https://en.wikipedia.org/wiki/Green_star_(astronomy) https://en.wikipedia.org/wiki/Green_star_(astronomy)
- leeoniya 4y agothe explanation is actually quite difficult to google. "why are plants green?" -> because chlorophyl "why is chlorophyl green?" -> because it reflects green and absorbs everything else okay, you have to search: "why did plants/chlorophyl evolve to be green"
- marginalia_nu 4y agoThis is tangentially related: https://youtu.be/36GT2zI8lVA https://youtu.be/36GT2zI8lVA
- alar44 4y agoYes, you need to search for the answer you are looking for.
- maven29 4y agoI think you have to skip Google and go for Google Scholar instead if you want to escape pop-sci publications and pointless blogposts.
- sh4rks 4y agoOr worse, Quora "answers"
- Silverback_VII 4y agoI always thought that it's because that they are descendants of a bacterium that was forced to use the less profitable part of the light spectrum(blue & red) because the main part was already occupied by other bacteria. By reflecting green from the sun, they reflect the strongest wavelength.
- fluoridation 4y agoThe peak of the solar spectrum seems to be in the blueish zone, though.
- 8bitsrule 4y agoYeah ... this line is misleading: "most of the energy that the sun radiates is in the green part of the spectrum." After filtering by the atmosphere, at the Earth's surface, blue and green energies are comparable. See e.g. the figure shown at [https://en.wikipedia.org/wiki/Sunlight#Spectral_composition_of_sunlight_at_Earth's_surface] https://en.wikipedia.org/wiki/Sunlight#Spectral_composition_...
- kzrdude 4y agoSo, are there multiple competing explanations being offered for this in general, and none of them have ever become entirely settled?
- leobg 4y agoI still don’t understand. How does specializing on blue and red remove the noise from flickering sunlight? After all, when it flickers (say, because of shades or clouds), doesn’t that affect all wavelengths equally? Why should green light be more unstable in that regard than blue and red?
- layer8 4y agoI didn’t quite get that either. It seems to be based on the fact that the intensity of sunlight varies with frequency: https://sunwindsolar.com/wp-content/uploads/2013/09/insolation-curve-adjusted.jpg https://sunwindsolar.com/wp-content/uploads/2013/09/insolati.... Green in the middle of the visible spectrum is the most intense, whereas blue and red fall of towards the edges of the visible spectrum, so are less intense. Maybe the noise is less for blue and red merely by virtue of those frequency ranges having less intensity.
- caper 4y agoI think it has actually more to do with "But they also needed to absorb light at different rates to buffer against the external noise caused by swings in light intensity." To create this buffering one would ideally have the the least proximal wavelengths, which will presumably be least similar in downstream rate of conversion/transportation and therefore smooth energy flow from the flickering, but which are still at near peak intensity. In this case that's blue and red visible light. The article notes they are at the steepest part of the intensity curve which is just a proxy definition for the above criteria. This of course still assumes that their model of generalised networks is analogous to the real biological cascades - otherwise could just be another coinciding superficiality rather than evolutionary reality (https://news.ycombinator.com/item?id=33050912 https://news.ycombinator.com/item?id=33050912). Quick skim through the source paper on SciHub leaves me sceptical.
- layer8 4y agoI think I need an ELI5 on that.
- acdanger 4y agoI read - I think here[0] - that green light doesn't penetrate water as well as other wavelengths. So there was no advantage to evolving to absorb the full spectrum. [0] https://press.uchicago.edu/ucp/books/book/chicago/H/bo16465693.html https://press.uchicago.edu/ucp/books/book/chicago/H/bo164656...
- aaaaaaaaaaab 4y agoThis doesn't explain why terrestrial plants didn't evolve some way to utilize e.g. UV radiation. It should be possible in theory, since we know of radiotrophic fungi: https://en.wikipedia.org/wiki/Radiotrophic_fungus https://en.wikipedia.org/wiki/Radiotrophic_fungus
- layer8 4y agoThe UV frequency range has much less energy in the solar spectrum than visible light, see here: https://sunwindsolar.com/solar-radiation-spectrum/ https://sunwindsolar.com/solar-radiation-spectrum/
- posterboy 4y agoIronic if those are the result of mutation caused by the UV radiation. If UV causes cancer in humans it's probably not good for fungi DNA. I think some indoor gardens do add low UV but I don't know exactly
- lightedman 4y agoJohn Lydon did some research with UVB radiation and cannabis that you might find interesting. This was done back in the 80s.
- moffkalast 4y ago> there was no advantage Well there is one disadvantage even: overheating.
- klabb3 4y ago> that green light doesn't penetrate water as well as other wavelengths As a diver that sounds weird. Red is the color that disappears quickly with depth. Blue is preserved the most. Additionally, land based plants have had some serious time to change color if more energy was beneficial, which clearly must be the case?
- Nomentatus 4y agoI think the necessary background fact here is that chlorophyll is a miracle chemical because it's safe. Not 'cause it's efficient. It's not efficient at splitting water, about 1%, but unlike so many other chemicals that can split water when hit with photons, it can perform the job while producing very few harmful free radicals. That's chlorophyll's secret sauce. Since green is a relatively high frequency that's intense in sunlight, it's safer to filter that color out. "Noise" here means a less smooth chemical process will produce more free radicals.
- blowski 4y agoFor the novices like me, whats the benefit in producing fewer free radicals?
- pid_0 4y agoFree radicals will cause cell damage and thus death or cancer
- smiley1437 4y agoFree radicals are extremely reactive and can form bonds in undesirable ways in cellular chemistry, which is generally bad for the organism, potentially causing all sorts of cell damage. Cells produce anti-oxidant defenses to regulate free radicals such as the delightfully named "Superoxide Dismutase" enzyme: https://en.wikipedia.org/wiki/Superoxide_dismutase https://en.wikipedia.org/wiki/Superoxide_dismutase
- anonymous_sorry 4y agoAs an aside, there is poor evidence that consumption or topical application of anything artificially high in anti-oxidants does any good for healthy people, although you see "antioxidants" used to sell crap all the time. Maintaining the right balance between free radicals and anti-oxidants is the sort of thing biology is pretty good at on its own. Trying to put a finger on the scales in one direction or another is probably pointless at best.
- osigurdson 4y ago>> There are plants that don’t appear green but… Seems like a fairly casual dismissal of data points that aren’t fitting the hypothesis.
- planetpluta 4y agoI think the rest of that sentence tries to explain the dismissal: >> There are plants that don’t appear green, like the copper beech, because they contain pigments like carotenoids. But those pigments are not photosynthetic: They typically protect the plants like sunscreen, buffering against slow changes in their light exposure The reason for non-green is not related to photosynthesis but some other process
- osigurdson 4y agoThis what I mean. The reason why some data points do not fit the hypothesis is thrown in rather casually, without any references.
- OhNoNotAnother1 4y ago
- sva_ 4y agoThere was a previous discussion on this: https://news.ycombinator.com/item?id=23998793 https://news.ycombinator.com/item?id=23998793
- imtringued 4y agoI have heard this theory. A plant that absorbs light perfectly would appear black and only the first few layers of cells would get any light at all. Chloroplasts only absorb a small portion of green light and reflect it so that the green light can penetrate deeper into the plant so that every cell gets some energy and even go through leaves and then be captured by a second layer of leaves so that the occluded leaves don't die.
- stevyB 4y agoSun emits the full spectrum of visible rays. The chlorophyl in the plant absorbs light with red and blue frequencies for photosynthesis and reflects the unused rest, this is what we see as green.
- eimrine 4y agoDo plants need a green light when growing in an artificial conditions?
- OhNoNotAnother1 4y ago
- fallingfrog 4y agoHas anyone plugged in the spectrum of a red dwarf star to see what color plants on a planet orbiting one would be? He states that the code is all available. I’m really curious.