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Carbon pathway, why is CO2 stability and pathways so important?

Discussion in 'Articles' started by Tom Barr, May 4, 2010.

  1. Tom Barr

    Tom Barr Founder
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    "In chloroplasts, limitation of CO2 fixation coupled with
    over-reduction of the electron transport chain(in other words, too much light) is the
    main cause of Reactive Oxygen Species(ROS) production."

    This leads to stress and reduced metabolic efficacy, reduced growth and stunting of growth if severe. This can occur over an hour or perhaps weeks etc, depending on the aquarist habits and set up.
    Perhaps the CO2 takes a long time to get non limiting when the lights come.
    Perhaps they think they have 40ppm when it's really 8ppm.
    Perhaps they think they have low light when it's really quite high.
    Perhaps their fish are stressed if they try and add more CO2, so they do not add enough, due to other factors like low O2, poor current etc.


    "Essential for ROS detoxification during normal metabolism, and
    particularly during stress, are antioxidants such as ascorbic
    acid and glutathione, and ROS-scavenging enzymes
    such as superoxide dismutase (SOD), ascorbate peroxidase
    (APX), catalase (CAT), glutathione peroxidase (GPX), and peroxiredoxin (PrxR) (Asada and Takahashi
    1987, Iba 2002, Mittler et al. 2004). These have been found in almost all cellular compartments, demonstrating the importance of ROS detoxification for cellular survival (Mittler et al. 2004)."

    From:
    http://www.plantstress.com/Articles/up_general_files/Reactive_Oxygen_2006.pdf

    When these systems are stressed further and limited strongly by CO2, this system cannot maintain itself and a cascade begins that leads to stunted growth. The plant can and may recover if good CO2 is added.

    CO2 is central to plant growth and metabolism.

    This is a good simple figure that explains the overall approach:

    http://www.agresponse.com/images/plantmetabolism.gif

    So what happens without CO2 or a limitation?
    Plants have suddenly much less energy, since the energy comes from the same things that we eat:
    carbohydrates, sugars, starch etc............

    If the plants suddenly lack Carbon to make the sugars, starches etc, then they have no food, like us, we get tired and go after our fat reserves. Plants do not have much fat reserves etc, but tend to translocate older leaves which act as their fat reserves.

    The other effect is no new growth at the active meristematic tips.
    Not enough CO2 to keep things going.

    Okay, say now you add more CO2 back...........it takes awhile for the metabolic pathways to re machine and get chugging along like they once where. Unlike say PO4 or N, that plants have extra of for a few days, CO2 runs out fast and is a much larger fraction of the total biomass, 40X more than N.

    It's not just the fixing of Carbon that needs up regulated once you bottom things out, it's also things like the mitochondria that produce the energy required for growth as well. These pathways can be quite long and involved. ROS(Reacive oxygen species) often damage many of the enzymes and machinery, compartments etc inside each cell when the CO2 is suddenly limited.

    Why does ROS play a role when CO2 is limited?
    Well, all that chemical reducing power that was suppose to go to reducing CO2 into sugar is left backing up, much like a traffic jam. Many of these ROS end up crashing into the machinery, destroying them. So even when the CO2 is added back, the effects are long and permanent. The cell has to make entirely new enzymes to process the CO2 and light.

    It's basically like pouring herbicides such as "diquat" at low levels on the plants.
    This herbicide decouples the electron transport in the light reactions and stops CO2 fixation.
    The ROS back up and start frying everything inside the chloroplast, so light and the the photosynthic pathway destroys the plant by blockage. CO2 limitation can do a milder effect.

    Given enough time to adapt and if the stress is milder, then plants can adapt to such CO2 changes.
    Slow mild changes can be tolerated fairly well. Plants can adjust and the ROS production is mild.
    Some plants are going to be worse than others at this adaptation, some will be heavily competitive compared to other species as well.

    So they will remove most of the CO2 limited supply, leaving very little for the other species.
    Since Carbon is the backbone for virtually all components in the plant cell, it makes good sense to treat it with the upmost respect and care. All the fats, cell wall, enzymes, membranes, all sugars, use massive amounts.

    Regards,
    Tom Barr
     
  2. argnom

    argnom Guru Class Expert

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    Ah, carbon. Is there something it cannot do?

    Thanks for posting this info Tom. It's appreciated as always.

    Cheers!
     
  3. Gerryd

    Gerryd Plant Guru Team
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    Great info Tom and nice to have the explanation of WHY the plants react as they do to co2....

    Isn't carbon in general considered one of the basic building blocks of life?

    Until they discovered all of the methane fixing bacteria at the bottom of the ocean, I think it was assumed that all life forms were carbon based...we just didn't know any better :)

    Or am I just remembering and confusing with an X files episode where they were talking about carbon based life forms?
     
    #3 Gerryd, May 4, 2010
    Last edited by a moderator: May 4, 2010
  4. Tom Barr

    Tom Barr Founder
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    Well, we eat carbon, plants gotta make it via CO2..........otherwise, like us not eating, things will not go well.

    Regards,
    Tom Barr
     
  5. Wet

    Wet Lifetime Members
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    Your teaching us using this comparison and analogy of plants as machines and element mass/metabolic processes as pathways is extremely helpful. Also helped in visualizing and getting a (I hope) better understanding of the linked text. I think this an effective teaching method for folks like me, fwiw.

    Thank you.
     
  6. Tom Barr

    Tom Barr Founder
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    Some get some of it, that's good enough. Folks may get it all some day, or not. No need to know every detail, as logn as the main idea is supported and seems logical.


    Think about algae in this CO2 content, we know they are never CO2 limited, but plants?
    Very often.

    So how is that going to affect the CO2 and carbon demand/supply and downstream metabolism between these two groups????

    I read all this hog manure about "There's so much we do not yet understand and know about Plants and Science" but these bozos cannot offer up any good ideas, hypothesis, background research, nor havwe they done a lick of homework background on the topics.....just some feel goodie BS. I'd like slap them with a mullet. They wanna yack yack.........but not doing anything.
    You keep hacking and chipping away at ideas and hypothesis, see what you can test and what you can falsify. Compare and see if folks have done this or that or falsified things/hypothesis. These clowns often wanna just make a few correlations and imply it's cause even when others come forward with examples that clearly falsify them. Nothing is that easy and simple, if it is, you are really lucky and as Einstein once said:

    "No amount of experimentation can ever prove me right; a single experiment can prove me wrong."

    Give that one a long ponder.

    These fools think they are smarter than Einstein.........heck, I'm plumb dumb, but I know it and realize I know much less than I use to think.
    I have to use logic and deduction, induction etc, analogies etc..........to help my feeble brain understand this complex stuff.
    The irony is the more you know, the less you know but the more you become aware of this fact. Emotionally unsettling, but intellectually beautiful.

    Always a trade off. Knowledge truly is infinite.

    Regards,
    Tom Barr
     
  7. Philosophos

    Philosophos Lifetime Charter Member
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    Thanks for the info and the article link Tom. I'd always wondered what the CO2 adaptation stress thing was about.
     
  8. TheKillHaa

    TheKillHaa Prolific Poster

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    Thanks Tom.

    i have a question, regarding CO2 amount/addition on a very low light planted tank:
    is there a low limit of light where adition of Co2 (lets say diy) is not worthly? or by contrary, no matter what, meanhwile we have living plants on our tanks we should provide extra carbon?

    hope i was clear enough, ;)
     
  9. Tom Barr

    Tom Barr Founder
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    Take a good look at the Tropica article and see what you think:

    http://www.tropica.com/article.asp?type=aquaristic&id=142

    If you think about allocation of resource, this means that adding CO2 at very low light will help the plant be able to survive on less light than would if you did not add CO2..........
    A better analogy would be to have fewer and fewer plants rather than adding less and less light for your case.

    With fewer plants, there's less demand for CO2 correct?
    Then light is independent and can be higher, but the CO2 not depleated since there's little plant biomass.

    I have Bolbtius in a CO2 enriched tank.
    I also grow it just fine, a bit slower(4-5X slower), in a non CO2 planted tank with few plants submersed.

    If I added a lot of Myrio to this non CO2 planted tank, kept the light and nutrients the same.....what do you think would happen?
    CO2 would go up? Down? Plant health of the Bolbitus? Growth rate of the Bolbitus?

    I think you get the idea.

    I think at some point, if you want to reduce the rates of growth down low, going non CO2 is simpler.......cheaper, less hassle etc..........but so is using CO2 at lower light, I'd say if you want the planting denser and chose any mix of species, wanta bit more growth than non CO2, then that's the main choice difference. They become fairly close when you get down far enough with the light, but you can use less light if you dose CO2/Excel than you could with non CO2.

    I think many assuem that if you have low light, you do not need CO2.
    Well, you do not need CO2 period.......... to have a planted tank, never did.
    We add it to get more from the light/have higher rates of growth, less plant= plant competition.

    Regards,
    Tom Barr
     
  10. TheKillHaa

    TheKillHaa Prolific Poster

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    thanks, i got the idea, very clear bytheway.
    cheers.
     
  11. Elohim_Meth

    Elohim_Meth Junior Poster

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    Doesn't it make sense to add some ascorbic acid, say with DIY micro solution? Are the plants able to assimilate it?
     
  12. Tom Barr

    Tom Barr Founder
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    Adding exogenous antioxidants does little, these are not animals.
    The antioxidants need to be at the sites of interest at the right concentrations made by the plant.

    We cannot amplify this much(if at all) by adding chemicals to the water etc........
    You can try(dump it it in and see, no one has seen anything however) , but if there's enough non limiting CO2 to begin with, then the plant can make a regulate everything just fine on it's own.

    My point is not to try and find some way we can add stuff, rather, the process involved and all the different asteps that need to be linked up, and not bouncing CO2 supplies up and down rapidly.
    This does little to algae since they are virtually neve rCO2 limited, but plants are very often. You basically have traffic jams and all sorts of havoc in each biochemical pathway when these things are disrupted.

    Regards,
    Tom Barr
     
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