Why don't plants absorb green light?

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Discussion Overview

The discussion centers around the question of why plants do not absorb green light, exploring the implications of chlorophyll's absorption spectrum and the evolutionary aspects of photosynthesis. Participants express curiosity about the mechanisms behind light absorption in plants and the apparent gap in the absorption spectrum between red and blue light.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants note the absence of light absorption in the green spectrum, questioning why plants reflect green light despite its abundance in sunlight.
  • Others suggest that chlorophyll, which appears green, absorbs red and blue light, leading to the reflection of green light.
  • A participant mentions the difficulty in finding peer-reviewed sources on this topic, suggesting that it is a well-known fact that plants absorb red and blue light but not green.
  • There are references to alternative theories, such as the "purple planet theory," which posits that early organisms may have used different chemical systems for photosynthesis that could have utilized green light.
  • Some participants express frustration over the lack of clarity in the original question posed and the need for better articulation of the inquiry to facilitate understanding.
  • A participant emphasizes the importance of providing sources to support claims and enhance the discussion, while others challenge the necessity of this requirement for a question.
  • There is a suggestion that the question of why plants reflect green light rather than absorb it is fundamental, even if no definitive answers are currently available.

Areas of Agreement / Disagreement

Participants generally do not reach a consensus on the original question's clarity or the necessity of providing sources. There are multiple competing views regarding the mechanisms of light absorption in plants and the implications of chlorophyll's properties, leaving the discussion unresolved.

Contextual Notes

Some participants express uncertainty about the original question's intent and clarity, indicating that assumptions about the audience's knowledge may affect the discussion. The exploration of alternative theories and the evolutionary context of photosynthesis remains open-ended.

AtomicJoe
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Seems odd there is a big hole in the spectrum between where they absorb red and blue light?
 
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AtomicJoe said:
Seems odd there is a big hole in the spectrum between where they absorb red and blue light?
Please provide a source so that everyone can be on the same page, thanks.
 
Evo said:
Please provide a source so that everyone can be on the same page, thanks.

Do I really need to provide a source to convince you that plants are green?
em_spectrum.jpg
 
Last edited by a moderator:
It's the rule. Please provide a source that explains your OP. Not everyone that reads these threads can read your mind.

Rules said:
Please clearly state what you wish to discuss. In general, one should attempt to flesh out questions and arguments adequately enough that readers will have a good understanding of the issue.

And by posting a source for your question, you would also find an answer, which is another good reason to flesh out your question with a preliminary search.

Why is it green?

We see because of light bouncing off things and getting into our eyes, the colour that bounces off is what it looks like. Chlorophyll looks green because it stores the red and blue light and bounces off the green and yellow light which go to our eyes. However this doesn’t make much sense – most of the light from the sun is yellow and green! So plants aren’t even touching most of the light they receive.
continued...

http://science-at-home.org/kid-question-why-is-grass-green/
 
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Evo said:
It's the rule. Please provide a source that explains your OP. Not everyone that reads these threads can read your mind.

It is a question, are questions forbidden?

Will this do?

http://www.ehow.com/facts_7530370_color-light-do-plants-absorb.html

It is difficult to find peer review stuff on such an obvious fact, ie that plants absorb red and blue, but not green light.

It is not the kind of thing which will win you the Nobel prize for biology!
 
AtomicJoe said:
It is a question, are questions forbidden?

Will this do?

http://www.ehow.com/facts_7530370_color-light-do-plants-absorb.html

It is difficult to find peer review stuff on such an obvious fact, ie that plants absorb red and blue, but not green light.

It is not the kind of thing which will win you the Nobel prize for biology!
For the sake of people that don't know what you are missing that prompted the question (especially when it's something taught in elementary school), you need to show a source so we can figure out where you are confused or not understanding. Anyway, I posted a very simple explanation for you above.

In other words, it's for everyone's benefit.
 
Plants don't absorb green because the molecule they use to absorb EM radiation is chlorophyll, which is itself green. Potentially another molecule could be used but this is how life evolved and having a different pigment molecule may be hard to evolve because of the necessary huge morphological difference i.e. thermoregulation.
 
Evo, I think you are being a bit hard on Joe, even if he does put his questions in a rather awkward way.

Assuming the question translated is:

Why do plants reflect the most abundant wavelengths (green/yellow) rather than use them for photosynthesis?

I thought this a very good question was motivated by this question to trawl the net since I don't know the answer either.

Firstly a search of PF itself didn't yield an answer.

Secondly I could cetainly find plenty of people asking this question on the net, but couldn't see one satisfactory answer, although one smart alec offered to email the 'true' answer if you emailed your attempt.

I found plenty of references to other potential chemical systems using other molecules, including one which used hydrogen sulphide not water as the mediator. This system is chemically favourable over chlorophyll/water and fors the basis of the purple planet theory.

Fourthly, I found plenty of references to the 'purple planet theory' that early organisms used anaerobic chemistry to photosythesise.

So I too would be pleased if some knowledgeable member would explain.
 
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  • #10
Studiot said:
Evo, I think you are being a bit hard on Joe, even if he does put his questions in a rather awkward way.

Assuming the question translated is:

Why do plants reflect the most abundant wavelengths (green/yellow) rather than use them for photosynthesis?

I thought this a very good question was motivated by this question to trawl the net since I don't know the answer either.

Firstly a search of PF itself didn't yield an answer.

Secondly I could cetainly find plenty of people asking this question on the net, but couldn't see one satisfactory answer, although one smart alec offered to email the 'true' answer if you emailed your attempt.

I found plenty of references to other potential chemical systems using other molecules, including one which used hydrogen sulphide not water as the mediator. This system is chemically favourable over chlorophyll/water and fors the basis of the purple planet theory.

Fourthly, I found plenty of references to the 'purple planet theory' that early organisms used anaerobic chemistry to photosythesise.

So I too would be pleased if some knowledgeable member would explain.
Firstly - it's the forum rules which Joe chooses not to follow.

Secondly - I posted an answer. It took me .05 seconds to pull it up in a google search. There was also an answer from a scientist at argonne, but it didn't go into as much detail.

http://www.Newton.dep.anl.gov/askasci/bio99/bio99087.htm

Asking questions is fine, but an effort should be made to provide some thought or background along with it.
 
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  • #11
With the greatest respect none of the posts here, or the links they contain, answer the question I posed.

Joe, since you are online perhaps you would confirm whether my translation is right or correct it if not?
 
  • #12
Studiot said:
With the greatest respect none of the posts here, or the links they contain, answer the question I posed.
I don't think you will find any better answers than the ones Ryan and I furnished.
 
  • #13
Studiot said:
With the greatest respect none of the posts here, or the links they contain, answer the question I posed.

Joe, since you are online perhaps you would confirm whether my translation is right or correct it if not?

No none of the post or links do answer the question.

I am not sure what you mean by 'my translation' (are you not english speaking normally).

No the links do not explain it, however I have a theory, but not allowed to post it (or indeed anything).
 
  • #14
I don't think you will find any better answers than the ones Ryan and I furnished.


Which is exactly what I said in my first post.

But I do find it interesting that life may not have originally carried out photosynthesis using more efficient chemistry which utilised the green light (reflecting the red and blue) and later switched to the green coloured chlorophyll using the red and blue and reflecting the green.

So I think it is a pretty fundamental question to ask why this was, even if we cannot at this moment provide and answer.
 
  • #15
Studiot said:
So I think it is a pretty fundamental question to ask why this was, even if we cannot at this moment provide and answer.
I have no problem with the question, it was how it was posted, it could have been posed much better in order to be clear to anyone that happened upon the post.
 
  • #16
I am not sure what you mean by 'my translation'

English is very definitely my native tongue.

As such I can tell you that your first post was not actually a question, even though it ended with a question mark.
So Evo was right to seek clarification.
I also think your response was an over-reaction.

Having seen several of your other threads develop like this I tried to introduce a bit of softening to re-establish focus for the benfit of all.
 
  • #17
ryan_m_b said:
Plants don't absorb green because the molecule they use to absorb EM radiation is chlorophyll, which is itself green. Potentially another molecule could be used but this is how life evolved and having a different pigment molecule may be hard to evolve because of the necessary huge morphological difference i.e. thermoregulation.


The problem is saying 'that is how life evolved' is not an answer because that does not explain how or why it evolved that way.

Eg saying giraffes have long necks because that is how they evolved is hardly a great answer.
 
  • #19
Studiot said:
English is very definitely my native tongue.

As such I can tell you that your first post was not actually a question, even though it ended with a question mark.
So Evo was right to seek clarification.
I also think your response was an over-reaction.

Having seen several of your other threads develop like this I tried to introduce a bit of softening to re-establish focus for the benfit of all.


My first post was:-
Why don't plants absorb green light?
Seems odd there is a big hole in the spectrum between where they absorb red and blue light?

The first line very definitely was a question, by anybodies definition surely?

The second line is actually a statement, but it is a statement posed as a question.

You still do not appear to have explained what you mean by "my translation"?

Note the above line is not a s straight forward question either but is again posed as a question in the unlikely event you did explain it but I failed to recognise the explanation.
 
  • #20
AtomicJoe said:
That's not a complete answer you have to explain why plants use chlorophyll also.
Why plants use chlorophyl is explained in my first link.
 

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