Why are plants green?

[esbo]

surely black would be better?

[Incendia]

I. Because plants contain chlorophyll - and chlorophyll is a pigment which reflects light which we interpret as green, whilst absorbing the light of different wavelengths.II. Why would black be better?

[esbo]

I. Because plants contain chlorophyll - and chlorophyll is a pigment which reflects light which we interpret as green, whilst absorbing the light of different wavelengths.II. Why would black be better?

 

I know the contain and chlorophyll is a pigment which reflects light which we interpret as green but the question is why do they contain chlorophyl?

There are plenty of other chemicals which can extract energy from the sun across the visible spectrum so why chose one which reflects green light

when it coudl be put to good use supplying energy to he plant?

[Fuzzwood]

Because it does not have anything to do with heat, but with photons of certain wavelengths. Quantum tunnel effects then cause the formation of sugars out of carbon dioxide and water. Just providing energy will not do anything. The cascade needs quantized amounts of energy for it to work.No-one ever stated it was efficient. Blame the cyano bacteria for this mechanism, then blame the ones that now make up your mitochondriae.

Edited September 15, 2011 by Fuzzwood

[esbo]

Because it does not have anything to do with heat, but with photons of certain wavelengths. Quantum tunnel effects then cause the formation of sugars out of carbon dioxide and water. Just providing energy will not do anything. The cascade needs quantized amounts of energy for it to work.No-one ever stated it was efficient. Blame the cyano bacteria for this mechanism, then blame the ones that now make up your mitochondriae.

 

Sorry but your reply was just waffle and nonsense, the is no explanation as to why plants are green as opposed to any other colour

in your reply. All your reply contains are a few big words to make you appear clever but as far as an explanation goes you post is null and

void. Are you aware of that? DO you actually believe your reply is a credible answer?????

[Hal.]

Green is what we see , if we were not sensitive to green light we might see a different colour . When Nitrogen is varied in plant foods the shades of green of the plant also vary . Some plants I have are missing a little calcium in their diet and some of the normally green leaves look a little purple .

[Essay]

Sorry but your reply was just waffle and nonsense,

?????

It only seems so because you don't know all the details surrounding that stuff, I suspect; but....

===

 

Briefly...

Plants are green because they mostly absorb redder light (reflecting more green as well as blue & yellow which also = green).

 

Red light is absorbed and used because it is high enough energy to provide usable "chemical" energy when gathered and distributed by the antenna-like pigments molecules... and more energy than just heat (IR)....

 

But Red light is not so "high energy" that is breaks the antennae apart. Look at what those shorter wavelengths do to organic molecules (especially the antenae-like resonators such as conjugated double bonds)... photo-oxidation.

 

This also explains why humus is not violet, blue, or green; but rather yellow, orange, or red; as those colors (bonding structures) can better survive the high energy of visible light.

 

~

[esbo]

Green is what we see , if we were not sensitive to green light we might see a different colour . When Nitrogen is varied in plant foods the shades of green of the plant also vary . Some plants I have are missing a little calcium in their diet and some of the normally green leaves look a little purple .

 

If we were not sensitive to green lick plants would appear black.

 

You answer is not really an answer, merely an observation, it does not explain why plants are green as opposed to any other shade of the rainbow.

 

It only seems so because you don't know all the details surrounding that stuff, I suspect; but....

===

 

Briefly...

Plants are green because they mostly absorb redder light (reflecting more green as well as blue & yellow which also = green).

 

Red light is absorbed and used because it is high enough energy to provide usable "chemical" energy when gathered and distributed by the antenna-like pigments molecules... and more energy than just heat (IR)....

 

But Red light is not so "high energy" that is breaks the antennae apart. Look at what those shorter wavelengths do to organic molecules (especially the antenae-like resonators such as conjugated double bonds)... photo-oxidation.

 

This also explains why humus is not violet, blue, or green; but rather yellow, orange, or red; as those colors (bonding structures) can better survive the high energy of visible light.

 

~

 

Saying they absorb red light is not an answer because they also absorb blue, which is at the other end of the spectrum.

Hence you argument about energy levels shatters into a thousand pieces because it absorbs light at both ends of the spectrum,

thus any argument which focuses on it favouring light above or below a particularly wavelength has a hole in it..

A big green hole just like the big green hole in the absorption spectrum of plants!!

 

Humus is part of the soil and hence no a plant so I don't know where you are going with that one.

[Essay]

Saying they absorb red light is not an answer because they also absorb blue, which is at the other end of the spectrum.

Hence you argument about energy levels shatters into a thousand pieces because it absorbs light at both ends of the spectrum,

thus any argument which focuses on it favouring light above or below a particularly wavelength has a hole in it..

A big green hole just like the big green hole in the absorption spectrum of plants!!

 

Humus is part of the soil and hence no a plant so I don't know where you are going with that one.

 

Why do you think plants absorb blue? How much?

I know plants absorb different colors depending on the time of year (fall colors) by using different pigments to channel the energy into the chlorophyl system, and blue may also be an ancillary pigment; but mostly it is the "green" pigment that is best at absorbing energy that is "low enough" to avoid destruction, and "high enough" to be more than simple heat.

===

 

btw....

Humus is derived from these same organic molecules, and so serves as an example of how destructive light is to organics. I was speaking of humus in freshwater (or even saline) sources, though it applys to soils also (but is not as obvious, as you noted). Interestingly, humus is about an order of magnitude greater than ozone, in its capacity to be protective from high-energy light, for developing or evolving life.

===

 

So is this idea still "shattered," or can you think of some questions to ask, or clarifications to seek?

 

~

Edited September 15, 2011 by Essay

[esbo]

Why do you think plants absorb blue? How much?

I know plants absorb different colors depending on the time of year (fall colors) by using different pigments to channel the energy into the chlorophyl system, and blue may also be an ancillary pigment; but mostly it is the "green" pigment that is best at absorbing energy that is "low enough" to avoid destruction, and "high enough" to be more than simple heat.

===

 

btw....

Humus is derived from these same organic molecules, and so serves as an example of how destructive light is to organics. I was speaking of humus in freshwater (or even saline) sources, though it applys to soils also (but is not as obvious, as you noted). Interestingly, humus is about an order of magnitude greater than ozone, in its capacity to be protective from high-energy light, for developing or evolving life.

===

 

So is this idea still "shattered," or can you think of some questions to ask, or clarifications to seek?

 

~

 

Plants absorb blue because we can see they don't reflect blue by the fact they look green.

Plants do no absorb any green light except then the leave are dead and decomposing.

This breakdown of the leaves structure cause them to absorb all colours as they breakdown into

carbon.

[Greg Boyles]

If we were not sensitive to green lick plants would appear black.

 

You answer is not really an answer, merely an observation, it does not explain why plants are green as opposed to any other shade of the rainbow.

 

 

 

Saying they absorb red light is not an answer because they also absorb blue, which is at the other end of the spectrum.

Hence you argument about energy levels shatters into a thousand pieces because it absorbs light at both ends of the spectrum,

thus any argument which focuses on it favouring light above or below a particularly wavelength has a hole in it..

A big green hole just like the big green hole in the absorption spectrum of plants!!

 

Humus is part of the soil and hence no a plant so I don't know where you are going with that one.

 

Who knows.

 

At the dawn of life on earth maybe there where cyanobacteria with energy absorbing pigments in them other than chlorophyll.

 

Perhaps there were purple, black and orange cyanobacteria.

 

But since none exist today we can assume that such alternative pigments were of little survival value in the evolutionary race.

 

Perhaps the chemical processes associated them were even less efficient than chlorophyll.

 

Perhaps by chance these other pigments were not stable in the presence of large amounts of oxygen.

 

Who the hell knows?

 

There is no way we can know, at least at present.

 

You could ask a million similar questions.

 

Why did fish evovle eyes? Why did primates evolve grasping hands?

 

We can only ask questions about the possible merrits of what we observe, but we can never really answer questions as to why what we observe came to be.

 

There have been far to many evolutionary steps between now and when those features first started arising.

 

You may as well ask why a particular rain drop came to fall on your nose.

[StringJunky]

I know the contain and chlorophyll is a pigment which reflects light which we interpret as green but the question is why do they contain chlorophyl?

There are plenty of other chemicals which can extract energy from the sun across the visible spectrum so why chose one which reflects green light

when it coudl be put to good use supplying energy to he plant?

 

One idea someone has come up with is that it is the colour best adapted to our Sun's colour temperature (including local atmospheric effects). On another planet with a local star that has a different colour temperature, chlorophyll may well not be the dominant pigment because it doesn't make the best use of that star's light so evolution there won't favour green.

 

http://www.ras.org.uk/news-and-press/217-news2011/1963-could-black-trees-blossom-in-a-world-with-two-suns

Edited September 16, 2011 by StringJunky

[esbo]

One idea someone has come up with is that it is the colour best adapted to our Sun's colour temperature. On another planet with a local star that has a different colour temperature, chlorophyll may well not be the dominant pigment because it doesn't make the best use of that star's light.

 

http://www.ras.org.u...d-with-two-suns

 

But the point is it is not the colour best adapted to the sun, the best adapted colour would be black so it could the full spectrum

of the suns energy, the question is why does only absorb a bit from each end, ie a bit blue and red but reflect the green in between those

two colours..

 

Who knows.

 

At the dawn of life on earth maybe there where cyanobacteria with energy absorbing pigments in them other than chlorophyll.

 

Perhaps there were purple, black and orange cyanobacteria.

 

But since none exist today we can assume that such alternative pigments were of little survival value in the evolutionary race.

 

Perhaps the chemical processes associated them were even less efficient than chlorophyll.

 

Perhaps by chance these other pigments were not stable in the presence of large amounts of oxygen.

 

Who the hell knows?

 

There is no way we can know, at least at present.

 

You could ask a million similar questions.

 

Why did fish evovle eyes? Why did primates evolve grasping hands?

 

We can only ask questions about the possible merrits of what we observe, but we can never really answer questions as to why what we observe came to be.

 

There have been far to many evolutionary steps between now and when those features first started arising.

 

You may as well ask why a particular rain drop came to fall on your nose.

 

 

WE know fish have eyes so they can find food and avoid predators, we know we have grasping hands

because they are good for climbing. Basic stuff.

Your premise that we will never understand why thing are is basically flawed, we understand pretty

much everything apart from why plants are green.

 

 

And that's weird.

[Greg Boyles]

WE know fish have eyes so they can find food and avoid predators, we know we have grasping hands

because they are good for climbing. Basic stuff.

Your premise that we will never understand why thing are is basically flawed, we understand pretty

much everything apart from why plants are green.

 

 

And that's weird.

 

That is not an answer esbo.

 

The golden mole, that has no functional eyes, is also equally profficient at avoiding predators.

 

And bats hunt at night using sonar rather than sight.

 

A possum, that does not have grasping hands, is equally proficiant, if not better, at climbing trees.

 

The point is that eyes and grasping hands are not the superior solutions to survival problems. They are just one of many and varied, and equally valuable, solutions.

[esbo]

That is not an answer esbo.

 

The golden mole, that has no functional eyes, is also equally profficient at avoiding predators.

 

And bats hunt at night using sonar rather than sight.

 

A possum, that does not have grasping hands, is equally proficiant, if not better, at climbing trees.

 

The point is that eyes and grasping hands are not the superior solutions to survival problems. They are just one of many and varied, and equally valuable, solutions.

 

Err... a possum does have grasping hands.

 

A bat does not have a big inexplicable hole in it's hearing spectrum as a plant does in it's energy absorbtion spectrum.

[StringJunky]

But the point is it is not the colour best adapted to the sun, the best adapted colour would be black so it could the full spectrum of the suns energy, the question is why does only absorb a bit from each end, ie a bit blue and red but reflect the green in between those

two colours..

 

Black is obviously no good on Earth for the reason Essay stated: "...but mostly it is the "green" pigment that is best at absorbing energy that is "low enough" to avoid destruction, ". It's a balancing act between maximising useful absorption and heat dissipation...a black plant obviously can't cope with or shed the excess heat or else they would be the dominant plants now.

 

Plants actually absorb 2/3 of the green part of the spectrum according to this article extract:

 

 

It is the absorbtion spectrum for chlorophyll that has been

extracted from a leaf. As you can see, although chlorophyll by itself

doesn’t absorb very well in the green wavelengths

(the low trough on the graph), the whole leaf has A > 0.5, so it absorbs

over 2/3 of the incident light in the green wavelength. Also, we must

consider that most plants are part of a "canopy",

where light first encounters tall plants, and then what isn’t absorbed by

the tallest plants goes down to the next level, and so on. So, eventually

almost all of even the green light is absorbed. The

wavelengths scanned here pretty much cover the visible spectrum.

Wavelengths shorter than this carry too much energy and can be actually

harmful, so the plant is better off reflecting them.

While longer ones do not have enough energy to be of much use chemically,

so absorbance of them would lead to excessive heating.

 

http://www.madsci.org/posts/archives/2000-03/952478790.Bt.r.html

Edited September 16, 2011 by StringJunky

[esbo]

Black is obviously no good on Earth for the reason Essay stated: "...but mostly it is the "green" pigment that is best at absorbing energy that is "low enough" to avoid destruction, ". It's a balancing act between maximising useful absorption and heat dissipation...a black plant obviously can't cope with or shed the excess heat or else they would be the dominant plants now.

 

Plants actually absorb 2/3 of the green part of the spectrum according to this article extract:

 

 

It is the absorbtion spectrum for chlorophyll that has been

extracted from a leaf. As you can see, although chlorophyll by itself

doesn’t absorb very well in the green wavelengths

(the low trough on the graph), the whole leaf has A > 0.5, so it absorbs

over 2/3 of the incident light in the green wavelength. Also, we must

consider that most plants are part of a "canopy",

where light first encounters tall plants, and then what isn’t absorbed by

the tallest plants goes down to the next level, and so on. So, eventually

almost all of even the green light is absorbed. The

wavelengths scanned here pretty much cover the visible spectrum.

Wavelengths shorter than this carry too much energy and can be actually

harmful, so the plant is better off reflecting them.

While longer ones do not have enough energy to be of much use chemically,

so absorbance of them would lead to excessive heating.

 

http://www.madsci.or...78790.Bt.r.html

 

I already said in my response to essay that his answer was flawed, so referring to his

answer is not very helpful.

Almost all green light is not absorbed, it is *reflected* so it does not go further down,

it can't as it is wanging it's way into outer space!!!!!

 

 

Your answer makes no sense, you say one lot of light has low energy so it is not

of much use, if that was the case why did the plant eveolve to absorb it.

Secondly you say the other bit of light is too damaging, however if that is the case why

has the plant evolved to absorbed it?

 

In short you answer has at least 3 humongous errors in it!! lol

 

You could not be more wrong!!!!!!

[StringJunky]

I already said in my response to essay that his answer was flawed, so referring to his

answer is not very helpful.

Almost all green light is not absorbed, it is *reflected* so it does not go further down,

it can't as it is wanging it's way into outer space!!!!!

 

Your answer makes no sense, you say one lot of light has low energy so it is not

of much use, if that was the case why did the plant eveolve to absorb it.

Secondly you say the other bit of light is too damaging, however if that is the case why

has the plant evolved to absorbed it?

 

In short you answer has at least 3 humongous errors in it!! lol

 

You could not be more wrong!!!!!!

 

I've given you someone's test data now give me yours.

 

Plant's have evolved with the best set of compromises.

Edited September 16, 2011 by StringJunky

[Essay]

I already said in my response to essay that his answer was flawed, so referring to his

answer is not very helpful.

Almost all green light is not absorbed, it is *reflected* so it does not go further down,

it can't as it is wanging it's way into outer space!!!!!

 

 

Your answer makes no sense, you say one lot of light has low energy so it is not

of much use, if that was the case why did the plant eveolve to absorb it.

Secondly you say the other bit of light is too damaging, however if that is the case why

has the plant evolved to absorbed it?

 

In short you answer has at least 3 humongous errors in it!! lol

 

You could not be more wrong!!!!!!

Or there may be 3 humongous things that you don't understand... But whichever, maybe we can figure it out....

Feel free to ask questions.

===

 

About the green light being "reflected" to outer space, the main point should be that it is "not absorbed" which means some or maybe most of it passes through, on down to the lower levels of the canopy or the ground. Only some is "reflected."

 

And really, plants don't absorb as much blue as they do red. I don't think you can grow a plant on strictly blue light, but strictly red will grow a plant. They do reflect blue (and yellow) so we also see that as green instead of blue (I may be wrong about that, but a physicist can correct me easily).

 

But overall we are thinking of chlorophyll as absorbing one wavelength, whereas in a real leaf there is an array of pigments which gather light energy of various wavelengths and channel it to the chlorophyll (assuming my decades-old plant physiology class is still valid); so that whatever angle the leaf is at, or however shaded it might be, it can get any sort of light and make use of it. It's just that red is mainly absorbed, so we see green (absorbed least) mostly around us.

===

 

But the point about the color of our star, and the energy it puts out, is the real answer to your question. That is what determines which chemicals will be photosynthetically effective yet still withstand the spectrum, and which would not be effective enough to drive chemical synthesis. Or if we were farther from the sun, plant life might be pink, in order to utilize the higher energy blues and greens; but at our current distance, blues and greens are too high in energy to absorb and utilize directly.

 

~

 

p.s. I notice the spectrum show a broad absorbance in the blue (400-480ish nm) and a sharp absorption peak in the red at about 680 nm. I wonder if that indicates a stongly "tuned" absorption in the red, contrasted with a less specific (less efficient?) more general absorption in the blue range; perhaps the higher energy blue overcoming the less specific (for blue) "tuning" of the antenna-like pigment molecules. Xanthine pigments in a leaf are tuned to absorb yellow most. Carotene, violaxanthin, and lutein absorb very little in the blue.

 

"Beta-carotene is best-known as the pigment of the carrot (Daucus carota). It occurs mostly as a crystal. One of its most important derivatives is vitamin A (a precursor of visual purple)."

http://www.biologie....ine/e20/20b.htm

 

see also: wikipedia says...

Violaxanthin is a natural xanthophyll pigment with an orange color found in a variety of plants including pansies. It is biosynthesized from zeaxanthin by....

Edited September 16, 2011 by Essay

[Greg Boyles]

Err... a possum does have grasping hands.

 

OK then a sloth does not have grasping hands but is none the less exceptionally profficient at climbing.

 

A bat does not have a big inexplicable hole in it's hearing spectrum as a plant does in it's energy absorbtion spectrum.

 

Each species of bat use very specific frequencies that its sonar operates at. So in effect they do have great unexplained wopping holes in their sonar systems. Think of all the additional information it could theoretically discern from its surroundings if it used multiple frequency sonar.

 

Obviously, despite the fact that logically to us it might seem beneficial, there is no evolutionary value to multiple frequency sonar in bats or it is not bilogically possible for some reason.

 

Same with principal with photosynthesis.

[Hal.]

 

If we were not sensitive to green lick plants would appear black.

 

You answer is not really an answer, merely an observation, it does not explain why plants are green as opposed to any other shade of the rainbow.

 

 

The light appearing on the surface of earth is not only made of shades of green wavelengths . The wavelengths of light not absorbed by the plant can be wavelengths other than those of green . The human eye is not only sensitive to wavelengths of green shades . So , if sunlight filtered of shades of green falls on the plant , that which is not absorbed by the plant and is also sensed by a human eye , would make a plant appear other than black .

[esbo]

I've given you someone's test data now give me yours.

 

Plant's have evolved with the best set of compromises.

 

Your absorption graph is a bit misleading here is a clearer one.

 

You are ducking the question when you just say it's the best compromise, you have to

explain why.

 

 

 

The light appearing on the surface of earth is not only made of shades of green wavelengths . The wavelengths of light not absorbed by the plant can be wavelengths other than those of green . The human eye is not only sensitive to wavelengths of green shades . So , if sunlight filtered of shades of green falls on the plant , that which is not absorbed by the plant and is also sensed by a human eye , would make a plant appear other than black .

 

Clearly plants are green, we can see that with our own eyes.

 

Thus the only thing which remains to be explained is why they are green and not red or blue or purple or orange.

Edited September 16, 2011 by esbo

[Hal.]

When people print ink on a piece of paper they put such huge numbers of dots together that from a distance it is impossible to distinguish one colour from another and our overall view is the intended shade . We have been tricked . If we could zoom in on a green plant would we only see green ?

 

 

[esbo]

When people print ink on a piece of paper they put such huge numbers of dots together that from a distance it is impossible to distinguish one colour from another and our overall view is the intended shade . We have been tricked . If we could zoom in on a green plant would we only see green ?

 

 

 

The point is plant are green and denying that is futile.

[Hal.]

I wouldn't deny plants are green , plants are also red , purple , blue , yellow , white , etc . The reason a plant is green can be viewed as a simple matter of the wavelengths of green light travelling from the sun to your eye . Nothing absorbed ( absorbed as in filtered ) the green shades on the journey and your brain is tuned to interpret it .