Why are plants green?

[esbo]

I question your assumption that the fact that plants do not absorb the green and yellow proportion of the visible spectrum means that photosynthesis is inefficient.

 

Clearly it is more efficient than the retinol system despite the fact that the cholorophyll system absorbs less of the visible spectrum than the retinol system.

 

Quite simple, if you absorb less them 100% of the available energy you are not 100% efficient.

 

Retinol is of little relevance to the issue.

[StringJunky]

I don't think I ever said "The physics of molecules with conjugated, double-bonded regions/structures, just doest favor developing a single way (molecule) for absorbing adjacent frequencies over a wide range of colors" Whether that is true or not is irrevelant. Secondly even if it were relevant you would have to show how it relates to my original post (you haven't). So a fair bit of work needed there.

 

Furthermore it is not remarkable to get two absorption peaks.

THe level of difficulty between adding 1+1+1 to get 3 is not signification greater than adding 1+1 to get 2.

 

I don't think you're putting any effort into absorbing the worthwhile contributions of some of the posters here...your question is about a highly speculative subject and it seems apparent that your mind is blinkered because you think you already have the answer.

 

Here's two more papers that argue green is the best colour overall. One examines the cost-benefit of green v black and the other ultimately because of the inherent inefficiency of an essential enzyme (rubisco).

 

Green Light Drives Leaf Photosynthesis More Efficiently than Red Light in Strong White Light: Revisiting the Enigmatic Question of Why Leaves are Green

 

Abstract

 

The literature and our present examinations indicate that the intra-leaf light absorption profile is in most cases steeper than the photosynthetic capacity profile. In strong white light, therefore, the quantum yield of photosynthesis would be lower in the upper chloroplasts, located near the illuminated surface, than that in the lower chloroplasts. Because green light can penetrate further into the leaf than red or blue light, in strong white light, any additional green light absorbed by the lower chloroplasts would increase leaf photosynthesis to a greater extent than would additional red or blue light. Based on the assessment of effects of the additional monochromatic light on leaf photosynthesis, we developed the differential quantum yield method that quantifies efficiency of any monochromatic light in white light. Application of this method to sunflower leaves clearly showed that, in moderate to strong white light, green light drove photosynthesis more effectively than red light. The green leaf should have a considerable volume of chloroplasts to accommodate the inefficient carboxylation enzyme, Rubisco, and deliver appropriate light to all the chloroplasts. By using chlorophylls that absorb green light weakly, modifying mesophyll structure and adjusting the Rubisco/chlorophyll ratio, the leaf appears to satisfy two somewhat conflicting requirements: to increase the absorptance of photosynthetically active radiation, and to drive photosynthesis efficiently in all the chloroplasts. We also discuss some serious problems that are caused by neglecting these intra-leaf profiles when estimating whole leaf electron transport rates and assessing photoinhibition by fluorescence techniques.

 

(Last Paragraph)

 

If a gradient in the ratio of Rubisco to photosynthetic pigments freely changes in response to PPFD, leaves could exist with black chloroplasts containing both chlorophylls and siphonaxanthin. When light absorption is plotted against the cumulative black pigment content for such leaves, the gradient would be very steep, because absorption coefficients would now be high for green as well as blue and red light. In the upper chloroplasts, the ratio of Rubisco to black pigments would then need to be very large but to decrease drastically with depth. Noting that the dynamic range of acclimational modification of chloroplast properties is limited within a given species, it would be impossible to counterbalance the profile of light absorption by drastically changing the Rubisco/black pigment ratio. It is, therefore, worth mentioning again that, by having chlorophylls with a ‘green window’ to the most abundant photosynthetically active wavelengths of solar radiation, green leaves have succeeded in moderating the intra-leaf light gradient to a considerable extent.

 

http://pcp.oxfordjournals.org/content/50/4/684.long

 

Cost and color of photosynthesis

Marcell A. Marosvölgyi and Hans J. van Gorkom

 

Abstract

 

The question of why plants are green has been revisited in several articles recently. A common theme in the discussions is to explain why photosynthesis appears to absorb less of the available green sunlight than expected. The expectation is incorrect, however, because it fails to take the energy cost of the photosynthetic apparatus into account. Depending on that cost, the red absorption band of the chlorophylls may be closely optimized to provide maximum growth power. The optimization predicts a strong influence of Fraunhofer lines in the solar irradiance on the spectral shape of the optimized absorption band, which appears to be correct. It does not predict any absorption at other wavelengths.

 

Intro

 

Introduction

Photovoltaic solar power converters are usually designed to absorb as much of the solar irradiance above the bandgap energy as possible, because maximum power output per surface area is considered to be most profitable. The photosynthetic solar power converters that maintain life on earth all have approximately the same characteristic absorption spectrum due to chlorophylls and carotenoids in their light-harvesting protein complexes. The existence of exceptions, spectrally different photosynthetic organisms adapted to the available irradiance at the bottom of the photic zone in deep or muddy waters (Stomp et al. 2007), merely adds weight to the question of why, at the top of the photic zone and especially on land, photosynthetic organisms are green, not black, in spite of two billion years of evolution.

 

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2807594/

Edited September 20, 2011 by StringJunky

[Ringer]

Quite simple, if you absorb less them 100% of the available energy you are not 100% efficient.

 

Retinol is of little relevance to the issue.

 

Alright, how about we try this a different way than you saying everyone's answers are wrong. If you can show that autotrophs could produce a substantially significant amount of ATP using all frequencies of visible light instead variety of visible and non-visible light we can really start to have an effective conversation the way you seem to want. Then you can show us how that would give it an advantage in reproduction compared to the extra energy the pigment containing cells it would need to produce upon what has already evolved.

 

You absorption argument is irrelevant, I could just as easily point out that predators only absorb around 1000th the energy available in its prey. Compared to autotrophs they are rubbish at efficiency. There is almost nothing evolution has made that is 100% efficient.

[Fuzzwood]

Indeed, evolution does not HAVE to create 100% efficient systems, just enough to cope with the environment a little better than other species, because that is what survives in the long run. And, who knows, maybe there were plants that absorbed all light, but that was actually a bad way to know it. That species of plant might not have lasted long enough to be found in fossils.

[Greg Boyles]

Indeed, evolution does not HAVE to create 100% efficient systems, just enough to cope with the environment a little better than other species, because that is what survives in the long run. And, who knows, maybe there were plants that absorbed all light, but that was actually a bad way to know it. That species of plant might not have lasted long enough to be found in fossils.

 

 

Even solar voltaics converts only about 30% of the incident electromagnetic radiation to electricity.

 

Since biological systems, including chlorophyll, are reliant upon quantum transitions of electrons to harvest some of the energy in sunlight and since quantum transitions can't just occur with any old wave length perhaps 100% harvest of visible light is simply not biologically possible with out a multiple parallel pigment systems. And the chance of such a system evolving is remote.

[esbo]

I don't think you're putting any effort into absorbing the worthwhile contributions of some of the posters here...your question is about a highly speculative subject and it seems apparent that your mind is blinkered because you think you already have the answer.

 

Here's two more papers that argue green is the best colour overall. One examines the cost-benefit of green v black and the other ultimately because of the inherent inefficiency of an essential enzyme (rubisco).

 

Green Light Drives Leaf Photosynthesis More Efficiently than Red Light in Strong White Light: Revisiting the Enigmatic Question of Why Leaves are Green

 

Abstract

 

The literature and our present examinations indicate that the intra-leaf light absorption profile is in most cases steeper than the photosynthetic capacity profile. In strong white light, therefore, the quantum yield of photosynthesis would be lower in the upper chloroplasts, located near the illuminated surface, than that in the lower chloroplasts. Because green light can penetrate further into the leaf than red or blue light, in strong white light, any additional green light absorbed by the lower chloroplasts would increase leaf photosynthesis to a greater extent than would additional red or blue light. Based on the assessment of effects of the additional monochromatic light on leaf photosynthesis, we developed the differential quantum yield method that quantifies efficiency of any monochromatic light in white light. Application of this method to sunflower leaves clearly showed that, in moderate to strong white light, green light drove photosynthesis more effectively than red light. The green leaf should have a considerable volume of chloroplasts to accommodate the inefficient carboxylation enzyme, Rubisco, and deliver appropriate light to all the chloroplasts. By using chlorophylls that absorb green light weakly, modifying mesophyll structure and adjusting the Rubisco/chlorophyll ratio, the leaf appears to satisfy two somewhat conflicting requirements: to increase the absorptance of photosynthetically active radiation, and to drive photosynthesis efficiently in all the chloroplasts. We also discuss some serious problems that are caused by neglecting these intra-leaf profiles when estimating whole leaf electron transport rates and assessing photoinhibition by fluorescence techniques.

 

(Last Paragraph)

 

If a gradient in the ratio of Rubisco to photosynthetic pigments freely changes in response to PPFD, leaves could exist with black chloroplasts containing both chlorophylls and siphonaxanthin. When light absorption is plotted against the cumulative black pigment content for such leaves, the gradient would be very steep, because absorption coefficients would now be high for green as well as blue and red light. In the upper chloroplasts, the ratio of Rubisco to black pigments would then need to be very large but to decrease drastically with depth. Noting that the dynamic range of acclimational modification of chloroplast properties is limited within a given species, it would be impossible to counterbalance the profile of light absorption by drastically changing the Rubisco/black pigment ratio. It is, therefore, worth mentioning again that, by having chlorophylls with a ‘green window’ to the most abundant photosynthetically active wavelengths of solar radiation, green leaves have succeeded in moderating the intra-leaf light gradient to a considerable extent.

 

http://pcp.oxfordjou...t/50/4/684.long

 

Cost and color of photosynthesis

Marcell A. Marosvölgyi and Hans J. van Gorkom

 

Abstract

 

The question of why plants are green has been revisited in several articles recently. A common theme in the discussions is to explain why photosynthesis appears to absorb less of the available green sunlight than expected. The expectation is incorrect, however, because it fails to take the energy cost of the photosynthetic apparatus into account. Depending on that cost, the red absorption band of the chlorophylls may be closely optimized to provide maximum growth power. The optimization predicts a strong influence of Fraunhofer lines in the solar irradiance on the spectral shape of the optimized absorption band, which appears to be correct. It does not predict any absorption at other wavelengths.

 

Intro

 

Introduction

Photovoltaic solar power converters are usually designed to absorb as much of the solar irradiance above the bandgap energy as possible, because maximum power output per surface area is considered to be most profitable. The photosynthetic solar power converters that maintain life on earth all have approximately the same characteristic absorption spectrum due to chlorophylls and carotenoids in their light-harvesting protein complexes. The existence of exceptions, spectrally different photosynthetic organisms adapted to the available irradiance at the bottom of the photic zone in deep or muddy waters (Stomp et al. 2007), merely adds weight to the question of why, at the top of the photic zone and especially on land, photosynthetic organisms are green, not black, in spite of two billion years of evolution.

 

http://www.ncbi.nlm....les/PMC2807594/

 

Can that lot be translated into English?

Without being rude it sounds like a load of bull to me, an attempt to use as many big words as possible do disguise the fact

that it says nothing useful.

 

Alright, how about we try this a different way than you saying everyone's answers are wrong. If you can show that autotrophs could produce a substantially significant amount of ATP using all frequencies of visible light instead variety of visible and non-visible light we can really start to have an effective conversation the way you seem to want. Then you can show us how that would give it an advantage in reproduction compared to the extra energy the pigment containing cells it would need to produce upon what has already evolved.

 

You absorption argument is irrelevant, I could just as easily point out that predators only absorb around 1000th the energy available in its prey. Compared to autotrophs they are rubbish at efficiency. There is almost nothing evolution has made that is 100% efficient.

 

Where did these autotrophs spring from?

Your response is similar to the one I described in my last post, just a bunch of words making little sense and lacking coherence to the OP.

 

Even solar voltaics converts only about 30% of the incident electromagnetic radiation to electricity.

 

Since biological systems, including chlorophyll, are reliant upon quantum transitions of electrons to harvest some of the energy in sunlight and since quantum transitions can't just occur with any old wave length perhaps 100% harvest of visible light is simply not biologically possible with out a multiple parallel pigment systems. And the chance of such a system evolving is remote.

 

There are lots of black surfaces in nature, your argument that they are too difficult to construct is ludicrous.

[Hal.]

That's English Esbo , complicated bull to you and to loads of others including myself . I don't have the necessary biological education to understand that and to examine some aspects and question the conclusions . From a light viewpoint I prefer to round off my opinion by saying the colour is what you sense . There are a lot of factors which affect it and if you want to concentrate on one or other , choose .

 

When I did some photography I took some photos of trees and on the negatives I was surprised at how the dark shaded side of plants had made nearly no impression ( very little light ) . People think leaves are green and a photographic negative tells me in shaded circumstances leaves are near black , people still say green .

[esbo]

That's English Esbo , complicated bull to you and to loads of others including myself . I don't have the necessary biological education to understand that and to examine some aspects and question the conclusions . From a light viewpoint I prefer to round off my opinion by saying the colour is what you sense . There are a lot of factors which affect it and if you want to concentrate on one or other , choose .

 

When I did some photography I took some photos of trees and on the negatives I was surprised at how the dark shaded side of plants had made nearly no impression ( very little light ) . People think leaves are green and a photographic negative tells me in shaded circumstances leaves are near black , people still say green .

 

Leaves are green it's beyond doubt.

Yes they look back in the dark, so does my light bulb when I switch it off.

Also negatives show the opposite of reality.

 

If you can't accept the obvious that plants are green what do you accept?????

[Laurens]

It's slightly unrelated, but if we had bright yellow plants would we get blue fruit?

 

I understood that fruit and berries evolved colours that were a high contrast against the green background (reds and oranges etc) so that animals could see them more easily...

 

I thought it would be cool to write a sci-fi book about a planet with yellow trees that produced blue fruit...

 

EDIT: Obviously I need to work that into a story somehow first

Edited September 20, 2011 by Laurens

[esbo]

My tobacco plants are yellow, lack of nitrogen I think.

[Hal.]

Esbo ,

 

I accept that the colour of an object is how it's seen .

 

 

[Greg Boyles]

There are lots of black surfaces in nature, your argument that they are too difficult to construct is ludicrous.

 

Really!

 

Black surfaces with the sole purpose of absorbing solar energy as opposed to providing camoflage!

 

Then name them Esbo!

[Ringer]

Can that lot be translated into English?

Without being rude it sounds like a load of bull to me, an attempt to use as many big words as possible do disguise the fact

that it says nothing useful.

 

 

 

Where did these autotrophs spring from?

Your response is similar to the one I described in my last post, just a bunch of words making little sense and lacking coherence to the OP.

 

 

 

There are lots of black surfaces in nature, your argument that they are too difficult to construct is ludicrous.

 

These responses show that you do not have the prerequisite experience or knowledge to understand an explanation any more complex that chlorophyll don't absorb green light so they appear green. If you honestly can't understand the link String Junky posted or what I said you just need to read an introductory Botany book. You can probably pick one up at a used book store for fairly cheap.

[Greg Boyles]

These responses show that you do not have the prerequisite experience or knowledge to understand an explanation any more complex that chlorophyll don't absorb green light so they appear green. If you honestly can't understand the link String Junky posted or what I said you just need to read an introductory Botany book. You can probably pick one up at a used book store for fairly cheap.

 

Clearly it is not only esbo's lack of biological knowledge that is a problem here.

 

Clearly his/her lack of understanding of quantum mechanics, which is behind the conversion of sunlight to chemical energy, is also preventing him/her from understanding the explanations that have been provided.

 

Also he/she obviously has little understanding of the constraints on evolution due to fixed genetic variability. The decendants of horses have no chance of sprouting wings and flying in the same way that the decendants of modern plants have no chance of developing a replacement for chlorophyll that converts more of the visible spectrum to chemical energy. There may be more chance of decendants of present autotrophic archae evolving into higher plants that are purple in colour.

[Ringer]

Clearly it is not only esbo's lack of biological knowledge that is a problem here.

 

Clearly his/her lack of understanding of quantum mechanics, which is behind the conversion of sunlight to chemical energy, is also preventing him/her from understanding the explanations that have been provided.

 

Also he/she obviously has little understanding of the constraints on evolution due to fixed genetic variability. The decendants of horses have no chance of sprouting wings and flying in the same way that the decendants of modern plants have no chance of developing a replacement for chlorophyll that converts more of the visible spectrum to chemical energy. There may be more chance of decendants of present autotrophic archae evolving into higher plants that are purple in colour.

 

His responses to my and others simple explanations seemed, to me at least, to hint at a lack of understanding in all these areas. But he needs to understand photosynthesis in a simple manner. Then he can move on to things like cellular respiration and photosynthesis at a cellular level with an understanding of how stomata, chloroplasts, and the like interact. Then he can move on to an understanding of the molecular side of things such as ADP/ATP transformation, the Krebs cycle, and the like. Then he might have the knowledge to appreciate the quantum mechanics of the system.

 

 

[StringJunky]

Can that lot be translated into English?

Without being rude it sounds like a load of bull to me, an attempt to use as many big words as possible do disguise the fact that it says nothing useful.

 

 

Just about all scientific papers are written in the form like the ones I linked. The reason lots of big words are used is for conveying the maximum amount of information in the smallest space and/or the shortest reading time. These papers are really written for other like-minded people that understand the lingo of a particular discipline and not the casual reader. Although I don't claim to fully understand all the implications of what each paper states, it is clear to me from these and what others have contributed here that black has too many problems to be taken on as a globally-prevalent light-gathering component, given other limitations of the external environment and within the leaf itself.

 

In two billion years, plants haven't evolutionarily found a better colour to use...it is the best fit for terrestrial Earth....that's why plant's are green.

Edited September 21, 2011 by StringJunky

[Greg Boyles]

In two billion years, plants haven't evolutionarily found a better colour to use...it is the best fit for terrestrial Earth....that's why plant's are green.

Technically 'a best fit' rather than 'the best fit'.

 

It is conceivable that some other pigment system, unknown to science, could have evolved. If modern plants did not evolve chlorophyll then would the chlorophyll molecule be known to modern science?

[esbo]

Clearly it is not only esbo's lack of biological knowledge that is a problem here.

 

Clearly his/her lack of understanding of quantum mechanics, which is behind the conversion of sunlight to chemical energy, is also preventing him/her from understanding the explanations that have been provided.

 

Also he/she obviously has little understanding of the constraints on evolution due to fixed genetic variability. The decendants of horses have no chance of sprouting wings and flying in the same way that the decendants of modern plants have no chance of developing a replacement for chlorophyll that converts more of the visible spectrum to chemical energy. There may be more chance of decendants of present autotrophic archae evolving into higher plants that are purple in colour.

 

I think you have got evolution a bit wrapped around you neck there.

Some early organisms developed into bird and some into horses.

 

Thus you need to explain why some early organisms did not develop into blue, red, black or orange plants.

 

Thus your comment about me not understanding biology is somewhat ironic under the circumstances.

 

Really!

 

Black surfaces with the sole purpose of absorbing solar energy as opposed to providing camoflage!

 

Then name them Esbo!

 

Black people's skin.

 

Need I go on? I don't think so!!!

 

Just about all scientific papers are written in the form like the ones I linked. The reason lots of big words are used is for conveying the maximum amount of information in the smallest space and/or the shortest reading time. These papers are really written for other like-minded people that understand the lingo of a particular discipline and not the casual reader. Although I don't claim to fully understand all the implications of what each paper states, it is clear to me from these and what others have contributed here that black has too many problems to be taken on as a globally-prevalent light-gathering component, given other limitations of the external environment and within the leaf itself.

 

In two billion years, plants haven't evolutionarily found a better colour to use...it is the best fit for terrestrial Earth....that's why plant's are green.

 

Well what I am looking for is why it is the best fit.

It is easy to understand scientific mumbo jumbo if it make sense, the trouble is it seems to be just mumbo jumbo without making any sense.

 

I am pretty sure if you showed me a similar science mumbo of another biological process which as as respiration or digestion or whatever I think I would be able to follow it. The trouble is, when things are wrong they do not usually make sense and I think in that particular case

the science 'mumjo' jumbo' is being used as a cover for the lack of a credible explanation.

Edited September 27, 2011 by esbo

[Greg Boyles]

I think you have got evolution a bit wrapped around you neck there.

Some early organisms developed into bird and some into horses.

 

Thus you need to explain why some early organisms did not develop into blue, red, black or orange plants.

No scientist can answer that question esbo. Science's primary purpose is to explain what we do observe. It is not to, and cannot be to, explain a million other scenarios of what we MIGHT be observing if evolution had run a different course.

 

One might as well try to detail what world history would have been had Nazi Germany had won WW2.

 

Thus your comment about me not understanding biology is somewhat ironic under the circumstances.

You either lack the education in these fields or you are simply being unnecessarily argumentative.

 

Black people's skin.

 

Need I go on? I don't think so!!!

 

And need I point out to you that animals have a totally different genetic make up to plants and are only remotely related in evolutionary terms. Just because animals produce melanin does not amount to proof that plants could ever have had the genetic capacity to produce melanin.

 

Genetics is not a total free for all where any organism can have any combination of genes from the total pool of genes across all life. Various genes in any given organism are often linked in various ways, e.g. sex linked charactersitics etc. They evolve collectively along with the physical characteristics they engender. And what might be possible with an animal population, genetically speaking, is limited by the genetic make up ancestors.

 

And even if plants arose that could produce melanin, there is no evidence that it could be substituted for chlorophyll and allow photosynthesis to operate at the same or greater efficiency, or even at all. The quantum mechanics of melanin molecules may simply not be suitable.

 

Well what I am looking for is why it is the best fit.

It is easy to understand scientific mumbo jumbo if it make sense, the trouble is it seems to be just mumbo jumbo without making any sense.

 

I am pretty sure if you showed me a similar science mumbo of another biological process which as as respiration or digestion or whatever I think I would be able to follow it. The trouble is, when things are wrong they do not usually make sense and I think in that particular case

the science 'mumjo' jumbo' is being used as a cover for the lack of a credible explanation.

 

It is mumbo jumbo to esbo because clearly you do not understand the concepts.

[StringJunky]

Esbo, we don't know...only various possibilities. As you are not able or at least not prepared to delve into the fundamental science there's no point continuing this. You can only skate on the the surface of a subject for so long before you have to get your head down into the hard stuff and that's where we are at now...the answer to the question is beyond simple analysis.

 

I'm inclined to think, like Essay, that full absorption is probably harmful in too many situations for plants to adopt black. This comment from a NASA geochemist which I've drawn from a link of Greg's seems to support this view as well:

 

David Des Marais, a geochemist at NASA's Ames Research Center in California, calls the purple Earth hypothesis "interesting," but cautions against making too much of one observation.

 

"I'm a little cautious about looking at who's using which wavelengths of light and making conclusions about how things were like 3 or 4 billion years ago," said Des Marais, who was not involved in the research.

 

Des Marais said an alternative explanation for why chlorophyll doesn't absorb green light is that doing so might actually harm plants.

 

"That energy comes screaming in. It's a two-edged sword," Des Marais said in a telephone interview. "Yes, you get energy from it, but it's like people getting 100 percent oxygen and getting poisoned. You can get too much of a good thing."

 

Des Marais points to cyanobacteria, a photosynthesizing microbe with an ancient history, which lives just beneath the ocean surface in order to avoid the full brunt of the Sun.

 

"We see a lot of evidence of adaptation to get light levels down a bit," Des Marais said. "I don't know that there's necessarily an evolutionary downside to not being at the peak of the solar spectrum."

http://www.livescience.com/1398-early-earth-purple-study-suggests.html

 

Which of all the hypotheses presented is correct? Take your pick.

Edited September 28, 2011 by StringJunky

[Ringer]

Esbo, do you know what chlorophyll do? Do you know how much energy is needed for the chlorophyll to manipulate ADP into ATP, and are you certain that the addition of wavelengths being absorbed could cause this reaction to be processed more efficiently? If so would you show us how it would do so?

[LawfulBlade]

Hi. Great question. As I haven't read every reply to this thread, my answer may be redundant.

 

The short answer is: no one knows for sure.

 

 

 

 

A slightly longer answer is that there are, in fact, additional known mechanisms in living things for converting light energy into a form that's usable to sustain life. Certain forms of archaea reflect the red portion of the spectrum, for example, and certain bacteria use blue and purple pigments instead.

 

Also, although they're still using chloroplasts (the makers of chlorophyll), there are leafy plants that are not green. Additionally, there are a few plants that don't make chlorophyll, and these aren't green.

 

There's a belief that the chloroplasts first entered the precursors to plant cells as an invading or accidentally acquired cyanobacteria that remained due to it being mutually beneficial (they're symbiotic). There's a similar hypothesis regarding the existence of mitochondria in animal cells. I've never heard one way or another whether the original cyanobacteria was supposed to be chlorophyll producing or not. Cyanobacteria themselves are blue, as the name implies, due to the pigment they use to gather light (rather than chlorophyll), so it must have evolved over time, if the original hypothesis of symbiosis is correct.

 

None of which answers the question of "why not black"? At this time, it's merely speculative, and is unlikely to ever be known. But at least I could help with the rest of your question.

[supersapien]

because animals like green juicy leaves

[Seiryuu]

I can't give an answer to the how, but I can tell you that you don't have to be the best to survive. You just have to be adequate enough. If you can survive, you will, until you bring consumption/competition into the equation...

[Phi for All]

Plants are green because the colour that bounces off them from sunlightand goes in our eyes is the colour green, the plant absorbs the entire rainbowcolours expect green that goes into our eyes and makes the plants look green!Hope my answer was helpful enough.

!

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