autumn colour

Discussion in 'Plants: Science and Cultivation' started by Dark Ant, Oct 22, 2006.

  1. Dark Ant

    Dark Ant Member

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    I understand why plants have green leaves but can anyone tell me why plants also have red, orange and yellow pigments in their leaves? What purpose do non-green pigments serve?
     
  2. pierrot

    pierrot Active Member 10 Years

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    Hello Dark Ant

    some of these secondary compunds play apart in plant protection eg anti fungal and anti viral compounds others are antioxidants such as flavonoids and anthocyanins. some arfe just things we have not yet found a function for. many are tannins that produce the flavourings for tea and other beverages.

    here is a basic explanation in this link

    http://scifun.chem.wisc.edu/chemweek/fallcolr/fallcolr.html

    you may want to look into the chemistry of secondary plant metabolism by searching for anthocyanins and flavonoids. lots of work has been done in this field by Jeffrey Harborne at U. Reading, Bruce Bohm and his lab here in Vancouver at UBC, Ken Markham at the DSIR in NZ and by Eckhard Wollenwebber in Germany.

    hope this helps you start your search
     
  3. petauridae

    petauridae Active Member

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    Many of those red, yellow, and orange pigments are compounds that aid in the photosynthetic 'machinery' of the plant. They can protect the plant from free electrons that must move through what is called the Z-scheme essentially by sacrificing themselves. (Free electrons that get 'loose' form what are called free radicals when the interact with compounds. By providing a 'sink' where they can end up and that is then sacrificed, i.e. discarded, that protects the plant). Another function is to aid in the trapping of light energy as chlorophyll, while really up to the task, cannot capture the most amount of light all the time. These compounds aid in that. The compounds I have been talking about are the carotenoids (orange/yellow) and the billins (some are red).

    The flavanoids and anthocynanins that the previous poster mentioned are typically found in flowers and fruits. I am curious that the link mentioned anthocyanins in leaves...I was not aware of this and I actually took a course from Bruce Bohm while I was in grad school at UBC. I guess I will have to look into this further!
     
  4. pierrot

    pierrot Active Member 10 Years

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    petauridae

    You are correct that large quantities of flavonoids and anthocyanins are found in fruit and flowers but the major amount of flavonoids are also found as exudates on leaves and as vacuolar compounds. that is why I and the article mentioned these as antioxidants as their ability to take free radicles from photosynthesis would mean they would have to be in the leaves. no?

    I too did courses with Bruce, he was my PhD Supervisor and my thesis was on vacuolar flavonoids in New Zealand Daisies.

    These compounds are also found in pollen grains and in one algae found by Markham and his associates In New Zealand (my Msc supervisor)

    Hope this helps
     
  5. Dark Ant

    Dark Ant Member

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    Dear Pierrot and Petauridae

    Thank you both for taking the time to answer me - and for such helpful answers too. I need to follow your research suggestions up.

    In the meantime a friend of mine sent me this link to an amazing site where they have made an animation showing how photosynthesis works. If you don't know it already, you might like it:

    http://vcell.ndsu.nodak.edu/animations/photosystemII/first.htm

    Petauridae, when you say "Another function is to aid in the trapping of light energy as chlorophyll, while really up to the task, cannot capture the most amount of light all the time. These compounds aid in that. The compounds I have been talking about are the carotenoids (orange/yellow) and the billins (some are red)."

    Does this mean the carotenoids and billins - through their colour - are capturing light from the centre of the light spectrum (ie green light) which is otherwise being reflected back off the green leaves?
     
  6. petauridae

    petauridae Active Member

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    Chlorophyll has two forms a & b (real creative, eh? There are also bacteriochlorophylls which are a bit different). These chlorophylls have two absorption bands: one in the red and one in the blue. Carotenoids only in the blue. The bilins absorb in the green and yellow. The purpose of these other pigments is to capture the light that chlorophyll cannot do so very well and then 'dump' it into the reaction centre of P680 (of the so called Z-scheme) via chlorophyll. So yes, you've got it!

    Pierrot--the biochemistry text I teach out of (Voet & Voet) makes no mention of anthocyanins in leaves, so what you say is new to me. Oh, and I did my PhD with RJ Andersen in the EOS/Chemistry depts at UBC.
     
  7. japa2222

    japa2222 Member

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    anthocyanins react with pH they turn red when the pH is more acidic and turn blue when pH is more basic. I'm pretty sure that'a outta my AP Bio text by Starr/Taggart.
     
  8. Dark Ant

    Dark Ant Member

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  9. petauridae

    petauridae Active Member

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  10. oscar

    oscar Active Member

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    A photon is Electromagnetic radiation (light) it is a "packet" (corpuscle) of energy, it has no charge and no mass and can travel at very high speed (the speed of light)
    Photons are created when an atom gets excited, heat and electricity can excite atoms, one of the electrons going around the atom gets pushed out of its regular orbit, into a higher orbit, when the electron snaps back into its proper orbit (not sure what causes the electron to snap back into its proper orbit) it releases a photon.
    Photon energy levels vary from the different atoms they have come from, sodium gives off yellow light, sort of, its energy at a certain frequency really, which we can see, recepters in our eyes collect the photons (a chemical reaction takes place in the eye, sending a signal to the brain telling the brain that, that frequency of photons matches to what we know as the colour yellow) we only see certain frequencies of light, we can feel infra red (just put your hand up to the sun and feel the warmth, thats infra red light) the pit viper sees infra red light (he sees the heat of infra red from the bodies of its prey) http://imagers.gsfc.nasa.gov/ems/infrared.html
    with plants certain frequencies are more useful than others they match the atoms of the atom that created the photon (im sure thats how it works) the photons energy gets collected by one atom and passed to another until it reaches an area close to the p680 thats when the electron seperates from the atom and starts the journey to help seperate the hydrogen and oxygen....i'll leave you to find out which photons match which atoms in the plant, as my head hurts from all this physics stuff.
     
  11. japa2222

    japa2222 Member

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    Doesn't the light ray hit the Thylakoid and causes the pigment inside that thylakoid to vibrate really fast until it loses an electron which shoots through the cell and causes the electron transfer train. Which opens and closes proteins that go into the cell. Then a water molecule inside the cell gives up an electron to the pigment which breaks the bond between the hydrogens and the oxygen which is why plants release oxygen, in the day. And this process followed by the calvin cycle produces the plant cells energy or ATP(it might be ADHP but i'm not sure).
    I'm not so sure about lights physical form because it is still debated over whether it is a wave or a particle, because it has properties of each.
     
  12. oscar

    oscar Active Member

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    now your entering into the realm of quantum electromagnetic dynamics, not an easy subject to get your head round.....but to answer your question, experiments have shown that light is particles (photomultiplier tests) but it does exhibit wave-like properties, i think you will find currently physicist agree that its a particle, more than 300 years ago they would say it was a wave....whos to say, in another few years, they might change their minds again....I tried to find the lectures by Professer Feynman, the Nobel prize winning physicist, who gives a very convincing lecture on properties of light and the experiments carried out to check that it is infact a particle (my browser seems to have lost it) anyway if you find an equally qualified physicist with experimental data showing light to be a wave, i'd be really interested.
    (even Feynmen confessed to not understanding the wave like properties)
    often you will see a photon represented as a particle with a wave-like symbol inside

    I dont think its the vibration that actually shakes off an electron...different atoms hold the electrons in varying orbits with greater or lesser attraction (gravity?) if you follow the link DarkAnt posted you will see at the core of the p680 is magnesium, a metallic element, i believe the metals hold their electrons in one of the highest orbits with the least amount of force from the protons and neutrons...which makes sence, a plant needing to use electrons to seperate hydrogen and oxygen, you'd want an electron that was easy to move....so i'd say it was something to do with the photons energy that forces the electron away from its proton and neutron.

    If anyone knows the whole process from start to finish, don't be shy, post it up.
     
  13. oscar

    oscar Active Member

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  14. japa2222

    japa2222 Member

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    You have got to admit that my response wasn't half bad for a 16 year old though.
     
  15. oscar

    oscar Active Member

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    I'd have never of guessed, its worth watching the lectures though its very interesting.

    If you figure out the mystery of the reflection of light, you might be the youngest Nobel prize winner.
     
  16. Dark Ant

    Dark Ant Member

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    thanks japa

    Is that how how hydrangea flowers turn blue?
     
  17. japa2222

    japa2222 Member

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    Flowers are different then leaves. Leaves do the work making energy. And flowers attract pollinators.
     

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