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Why those additional pigments?

Discussion in 'General Plant Topics' started by essabee, Dec 24, 2009.

  1. essabee

    essabee Prolific Poster

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    Why do certain species of aquatic plant colour up under intense light? That they do is something we often observe in all well lighted planted tanks. That this change in colouration becomes more prominent with the intensity of light is also a common observation. I will concede that some specie of aquatic plants will not show any perceptible change in their colouration and some others do not need very intense light to be other than green.

    There are and always had been nutritional factors which can change the colouration of plants – but those need not be addressed here.

    As I see it, when a plant does change its colour under lights, it does not stop reflecting the green part of the light spectrum it normally did, but is now reflecting an additional part of the spectrum, and this causes the change in colouration. Conversely this means that the plant is reducing the range of the light spectrum it was absorbing. Therefore it follows that the plant is reducing its energy absorption from those parts which are in more intense light. Why?

    Additional energy when there is no lack of nutrients for the plant to increase synthesis of its growth substances should have been an advantage to the plant; still the plant is opting to reduce it energy absorption. Nature never induces curtailment of any action (or omission) which is of advantage to any specie; then why is such an advantage to the plant being curtailed? The answer must be that behind the obvious advantage lies some hidden disadvantage.

    Reflecting over the question, it suddenly struck me the answer must be oxygen. Oxygen is synonymous with life, as we know it, but it is a dangerous poison. Man regularly uses oxygen and oxidising agents to kill living organisms. The most abundant byproduct of photosynthesis is oxygen. Therefore the plants that change colour with more intense light must have a limited capacity to handle the byproduct oxygen in its photosynthetic action. The change of colour is a defensive mechanism to reduce the quantum of the byproduct – oxygen.

    I am no scientist, but I do like my queries answered. So I put questions to myself and try to find logical answers to them, not all my beliefs are true but this time I think I am on the right track.

    Nature does nothing without reason. The propensity to change colour must have a purpose, especially as synthesising those pigments need effort and expense of nutrient elements of these plant specie. No plant would evolve such an unnecessary and costly (extravagant) behaviour.

    Genetically the threshold of different plants in handling of oxygen or the mechanism by which different specie control the threshold may differ. The explanation why some plants do not change colour would be there.

    The range of the spectrum chosen by the plant would naturally be fixed by their genetic evolution.

    Even if the trigger for additional pigments is linked to the byproduct oxygen from photosynthesis only; it would explain nutritional deficiencies and/or availabilities causing colour change in plants.

    Any nutritional deficiency which affects the plants efficiency in handling the oxygen – or a nutritional excess of any element that increases the plants photosynthesis; can and will cause a change of the colour of the plant, when the threshold is breached.
     
    #1 essabee, Dec 24, 2009
    Last edited by a moderator: Dec 25, 2009
  2. nipat

    nipat Guru Class Expert

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    I've seen many researches say that very intense light (much more intense than what we use with our tanks)
    can reduce algae growth rate or even kill it by overloading its photosynthetic apparatus.

    May be plants doing this for the same reason?
     
  3. ordloh

    ordloh Prolific Poster

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    I think the misconception is that more intensely colored plants reflect more light. Actually, absorption is what causes colour. The more intense the color we perceive, the more light is absorbed. So when a plant changes color from green to red, it does not reflect more red then it previously did, rather it absorbs more green. So energy intake is increased by additional pigments.
     
    #3 ordloh, Dec 25, 2009
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  4. nipat

    nipat Guru Class Expert

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    I didn't really think about the word ‘additional pigments’ when I replied.
    From what he (essabee) wrote, he seemed to know the idea of reflection/absorption but might use the wrong word.

    I don't think plants changing color from green to red always means that they absorb more light.
    How about darker, more intense green vs brighter, paler red?

    I look at jeff5614's picture (the first one).
    http://www.barrreport.com/showthread.php/6752-Need-high-light-for-red-plants-1-8W-gal-see-what-you-think

    The short stems below are greener and they seem to reflect less light (look darker)
    than the higher stems (which are brighter or pale...red). And human vision is more
    sentitive in green. So what seems to be bright green may actually be darker in reality.
     
    #4 nipat, Dec 25, 2009
    Last edited by a moderator: Dec 25, 2009
  5. ordloh

    ordloh Prolific Poster

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    yup that's true. However my point was more like, additional pigments increase absorption rather then decrease it.
     
  6. essabee

    essabee Prolific Poster

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    Take a tank fill it up with very clear water and attach charcoal black paper to the outside of three sides. Now light this tank from the top with as intense a light that you can use. There are no pigments in the water and therefore you will see it to be dark inside the tank.

    You see that you need pigments to reflect light, yes they do absorb certain portions of the spectrum but they turn back at you a certain portion too - they are like coloured reflectors. Brighter colours mean very little is absorbed.
     
    #6 essabee, Dec 25, 2009
    Last edited by a moderator: Dec 25, 2009
  7. ordloh

    ordloh Prolific Poster

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    well, the charcoal black paper has pigments. I'm not really sure what you're talking about. Water does not absorb visible light hence it is colorless, ie transmittance of visible light is maximum. Transmittance and reflection are both simply caused by light not being absorbed. You do not need pigments to reflect light, all atoms reflect light that are not absorbed/passed through them.
    All molecules absorb light, colorless ones like water, NaCl etc absorb outside of the visible portion. Hence they are colorless. Pigments are molecules that absorb inside the visible portion.
     
  8. Tom Barr

    Tom Barr Founder
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    Then you will want to be specific about which plants you speak of, and not generalize.


    The plant still absorbs the light and different spectrums, this can be measured by the reflecting light and spectroradiometer for each nm wavelength in question.
    Absorption and our preceptions of light are very different, you cannot make this observation and use it as support for this conclusion.
    You must measure it.

    It may have nothing to do, with this "dis/advantage", plants in nature have to adapt to a much wider range of conditions, light changes hour tpo hour, day to day, even second to second as light filters through a forest canpoy.
    These flecks of light cause very high levels and very low levels to strike the leaf. Which set of pigments would it use there then?
    The situation is both cases.

    Plants can and do adapt.
    But they also have mechanisms for each case. It's often not "either" "or", rather.........both cases that we find.

    So adding pure O2 would change the colors of the plants?
    Have you tired this? I have with algae, no results at 150% O2 and with any CO2 combination relative to low O2(90-100%).

    Since O2 ppms are correlated with growth rates of submersed plants,, how can it be due to O2 vs a general growth rate?
    You can test it by adding O2 to these same levels.

    Then why do you have an appendix?
    Why do whales have a hip bone?

    Obviously, we do not need them and they impart no advantage.

    Evolution in the aquarium or nature?
    Where are we talking about?

    Very important point.

    I suspect teasing apart growth rates and O2 due to color pigment change is fairly straight forward test.
    But.........you'd need to look up how O2 and growth rates change things in a steady light state and with enriched CO2.

    Growth is a huge factor there and O2 makes little difference if the growth is not also addressed.

    Regards,
    Tom Barr
     
  9. essabee

    essabee Prolific Poster

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    Adding oxygen to the water will have no effect as it will not cause damage to the plant tissue surrounding the photosynthetic area. Then again the reactions taking place during photosynthesis may be producing oxygen (or to a certain extent of the oxygen) in its nascent form which causes the damage.

    Your reply appears to be directed more against me and not the subject of my post. Just look at the arguement

    "Then why do you have an appendix?
    Why do whales have a hip bone?

    Obviously, we do not need them and they impart no advantage."

    Any child, aware of Darwin's work, will tell you why we have an appendix or the whales have hip bones.

    My post is not the result of any experiment or a scientific research but a thought about what goes on around us. Being an aquarium plant forum and the subject being thoughts about aquarium plants, I have shared it with others having the same interest. If such conversations are not allowed I shall correct myself and refrain from speaking about my thoughts here.

    Thank you Tom Barr
     
  10. ordloh

    ordloh Prolific Poster

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    This is hardly a discussion, you're pretty much telling us how it is.
     
  11. Tom Barr

    Tom Barr Founder
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    There is a difference between an idea and a person.
    Debating what the merits of an idea are/are not is vastly different from personal gibberish, assumptions about others and their intent and actions.
    I can make statements of ideas that are without merit, or show I have not done my homework. However, it does not imply anything about myself/you personally.
    I go after the idea, never person, that is an assumption you made, if it was not clear .........simply ask.
    In person, these types of exchanges virtually never occur, over the web, many folks obsess and read into things much more than they really should.
    Take things with a grain of salt in otherwords.

    http://www.littlersworks.net/reprints/Littler1979a.pdf

    See fig's 1-3, clearly O2 concentration has a strong affect.

    For plants, and the issue with Darwin............all plants use Rubsico to fix CO2 from the external environment. O2 comes in and is also fixed and these two processes are in fact concentrationally dependent.
    Rubsico is an old enzyme back when the air was richer in CO2 and low in O2, this has changed over time.

    In response, plants and algae both have developed ways to deal with O2 toxicity both internally and externally. Photorespiration is a strong inhibiting factor in many species including macrophytes.
    In response to this, C4 plants developed. Corn etc..........many if not most of the crops are C4 plants that concentrate the CO2 around the Rubsico to advoid PR.

    But............not all plants do this, and the same is true for aquatic plants.
    Algae use another method to address it, but not all algae do this either.

    http://www.plantphysiol.org/cgi/reprint/58/6/761.pdf
    http://www.plantphysiol.org/cgi/reprint/73/2/488

    Both are excellent papers to think about for PR and O2/CO2 issues.

    I think you would get much farther by looking things up, and seeing what is out there.
    Such research and papers will offer much more support and guide you better on how to develop your own test so you may answer things and share such results with others.

    Do not get distracted with personal stuff. Stick to the topic.
    If you have an interest in this and other topics, ask and I'll provide some good papers to review.

    http://www.plantphysiol.org/cgi/content/abstract/73/2/488

    Dr Bowes is excellent for the O2/CO2 issue with aquatic plants and algae, he discovered PR and was an old past professor of mine. I know this topic somewhat well.

    A google scholar look shows for macrophytes AND PR:

    http://scholar.google.com/scholar?hl=en&q=+photorespiration+macrophytes&btnG=Search&as_sdt=2000&as_ylo=&as_vis=0

    You will find plants that have no effect with increased O2, others will, same for algae.





    If personal gibberish is what you want, go to a social networking site.
     
  12. essabee

    essabee Prolific Poster

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    ^ this answer is greatly appreciated by me. This what I was looking from you at the first instant (sans the very natural anger at my coment ofcourse).
     
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