Why are plants green?

Discussion in 'Earth Science' started by esbo, Jul 20, 2011.

Thread Status:
Not open for further replies.
  1. Trippy ALEA IACTA EST Staff Member

    Messages:
    10,890
    Your question is based on a false premise.

    Chlorophyll is not the only pigment used by plants to extract energy, it's not even true of green plants. Green plants use a range of accessory pigments in conjunction with chlorophyll, specifically to harvest light energy and convert it to something useable, they include:
    Carotene - an orange pigment
    Xanthophyll - a yellow pigment
    Phaeophytin a - a gray-brown pigment
    Phaeophytin b - a yellow-brown pigment
     
  2. Google AdSense Guest Advertisement



    to hide all adverts.
  3. Trippy ALEA IACTA EST Staff Member

    Messages:
    10,890
    This is beginning to smell like creationist trolling (it also sounds like a 'No True Scottsman' Fallacy).

    You're going to have to explain how you define a 'true leaf' because (for example) Poinsettias only have one kind of leaf, and they're red.
     
    Last edited: Jul 20, 2011
  4. Google AdSense Guest Advertisement



    to hide all adverts.
  5. Trippy ALEA IACTA EST Staff Member

    Messages:
    10,890
    Retinal was (and still is) the colour it is because the total length of the conjugated double bond system matches the wavelength of a photon with a wavelength of around 400nm, and so Retinal can absorb photons of this wavelength, and in so doing is excited into a higher energy electronic configuration, however because Retinal absorbs in the blue-green part of the spectrum, it appears red-orange to us. It appears red-orange to us, because our eyes see in three colours (red, green, and blue) or in a very few cases four (predominantly women). Our brain then 'adds' the strength of the responses in these three bands and 'calculates' the colour it is seeing.

    We see it as Orange, because what we're seeing is mostly red with a little bit of green and no blue.

    Attaching the Retinal to other stuff, as it would have to be to be useable by plants, changes (lowers, in this case, I believe) the wavelength of light that is absorbed, by changing the length of the conjugated double bond system, resulting in a slightly different colour.

    EG:

    Please Register or Log in to view the hidden image!



    This is why Rhodopsin (what things using Retinal to make food use) is purple.
     
    Last edited: Jul 20, 2011
  6. Google AdSense Guest Advertisement



    to hide all adverts.
  7. esbo Registered Senior Member

    Messages:
    84
    What make you think it is creationist?

    I fail to see the link?

    Could you explain how you made that connection?
     
  8. esbo Registered Senior Member

    Messages:
    84
    It goes without saying that retinal has the chemical properties that make it appear the colour it is, that is a trivial argument.


    I mean it would be a shocker if it had chemical properties which made it appear different colour to what it was.

    Intact it would be a miracle!

    It's like saying:

    Q: Why did the man cross the road?

    A: Because he used his legs to transport himself to the opposite pavement.
     
  9. Trippy ALEA IACTA EST Staff Member

    Messages:
    10,890
    This is a bait and switch - whether or not I think you're a creationist is irrelevant to the discussion.

    I posed you a legitimate, relevant, question, "What do you define as a true lead". And you're using the point that I expressed the opinion that your posts were starting to sound like creationist trolling as a distraction to avoid answering it.
     
  10. Trippy ALEA IACTA EST Staff Member

    Messages:
    10,890
    So then the answer to your question "Why is Retinal purple" is "Because of its physico-chemical properties", and you accept that as an answer.
     
  11. esbo Registered Senior Member

    Messages:
    84
    Sounds to me like you are trolling mate.

    Unless you can explain your creationist point I don;t see why I shououdl answer, however I will.

    I don't think you yourself know why you made the creationist point and that's probably why you can't make an answer. OR at least in trying to say why you realised how stupid your point was.

    Anyway I am not interested in one or two obscure plants I am interested in the other 99.9% of plants.

    I can change my question to "most plants" rather the "plants" is you are going to nit-pick.
     
  12. esbo Registered Senior Member

    Messages:
    84
    Only in the most trivial sense.

    It is not an answer in the context of the question I originally asked.
     
  13. origin Trump is the best argument against a democracy. Valued Senior Member

    Messages:
    10,000
    Have you got some sort of problem? When someone asks a question it usually is because then are seeking an answer. Sometime it is because they are seeking a confrontation. You seem to be of the latter.

    It would seem that you have a view point on this; perhaps you could try being honest and share your view.

    Or you can buzz off, I personally don't feel like playin your little game....

    Please Register or Log in to view the hidden image!

     
  14. esbo Registered Senior Member

    Messages:
    84
    I think you should forget the all the personal issues you have about the question and just see it for what it is, a question.

    If you can answer it fine, if you can't that's fine too.
     
  15. MacGyver1968 Fixin' Shit that Ain't Broke Valued Senior Member

    Messages:
    7,028
    Plants are green because it's god's favorite color.
     
  16. esbo Registered Senior Member

    Messages:
    84
    How do you now he has a favourite colour?
     
  17. MacGyver1968 Fixin' Shit that Ain't Broke Valued Senior Member

    Messages:
    7,028
    It was a joke...I'm an atheist.

    Please Register or Log in to view the hidden image!



    I'm not a biologist...but if I had to try to answer your question about why plants use chlorophyll and not some other chemical, is because billions of years ago, some "proto-plant" first used chlorophyll and was highly successful and prospered while others did not. It survived and gave rise to all other chlorophyll using plants, as it was such a beneficial mutation.
     
  18. Trippy ALEA IACTA EST Staff Member

    Messages:
    10,890
    No trolling involved, on my behalf at any rate.

    I've already explained that it's not directly relevant, simply an opinion reflecting on the language you've used so far. Move on.

    This, is trolling. Not to mention ridiculous. I know exactly why I made the comment, and won't answer is not the same as can't answer. One does not imply the other.

    Which would be great if I were only talking about a minority of plants, but I'm not.
    EVERY SINGLE PLANT, for example, contains caretenoids of some form, to some extent. The also contain each and every single on of the other pigments I named, in varying degrees and combinations, this is why plants are so many different shades of green.

    Your question has been answered, however.
    Q: Why are plants green?
    A: Because of Chlorophyll.

    Q: Why is Cholorphyll green?
    A: Because Chlorophyl contains a cyclic conjugated double bond system, which has a magnesium ion bound to it (as a ligand). It's green because the total length of the conjugated system matches the wavelength of a red photon.

    Q: Why do modern plants use Chlorophyll for photosynthesis?
    A: Perhaps Plants using chlorophyll had to compete with plants using pigments that absorbed in the green portion of the spectrum, and chlorophyll outcompeted them because it was more efficient at converting energy into food.
    Perhaps the over abundance of energy in the part of the spectrum is detrimental.
    Perhaps the different atmospheric chemistry of the early earth (at the time Autotrophs evolved) scattered and absorbed light differently from what is observed now - resulting in red light being the most widely available light source at ground level.
    Perhaps absorbing only low energy radiation reduced early mortality - the early atmosphere may have been a lot more transparent to Higher energy frequencies, which do more damage (this is related to why colours fade with time). This has the advantage of explaining why plants incorporate the auxillary pigments they do - they all absorb strongly in the UV/Blue end of the spectrum, some of them have anti-oxidant properties, and none absorb in the green portion. This has the net effect of protecting Chlorophyl from the damaging high energy radiation (Chlorohyll also absorbs in the Blue/UV part of the spectrum), as well as protecting it (and the rest of the cell) from the effects of damage that is done.
    Perhaps a combination of all of the above.
    Perhaps none of the above - at this point, all we can really do is speculate, and through that speculation we can't rule out the existence of multiple photosynthetic pathways in the early history of the earth, using a variety of pigments, the only thing we can say for certain is that there was some environmental factor that meant that those organisms using chlorophyl based photosynthesis were more successful than the others.

    Q: Why aren't the pigments that plants use black?
    A: Because pigments that absorb across the whole electromagnetic spectrum degrade very quickly (related to the penultimate point above).
     
  19. spidergoat Valued Senior Member

    Messages:
    51,949
    It's the color that's most easy on our eyes. (This was the answer that made Christopher Hitchens into an atheist, when he heard it from his school teacher).
     
  20. adoucette Caca Occurs Valued Senior Member

    Messages:
    7,829
    Why do I get the strong feeling that esbo will say this excellent answer is also wrong?
     
  21. esbo Registered Senior Member

    Messages:
    84
    So why were they highly successful?

    Care to explain?
     
  22. Me-Ki-Gal Banned Banned

    Messages:
    4,634
    That is what I was thinking , A Creationist bate and switch
     
  23. Ellie Banned Banned

    Messages:
    424
    ewwww...telling jokes about *od?

    Macky i give spanky

    :spank:

    Please Register or Log in to view the hidden image!

     
Thread Status:
Not open for further replies.

Share This Page