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Concentration & Uptake

Discussion in 'General Plant Topics' started by abcemorse, Aug 31, 2009.

  1. abcemorse

    abcemorse Prolific Poster

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    All other things--light, CO2, etc--being equal, does the concentration of a given nutrient affect the rate at which it is taken up by the plant?
     
  2. Philosophos

    Philosophos Lifetime Charter Member
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    I'm not an expert with this one, but I'd imagine there's only so fast that active transport mechanisms within plants can process nutrients at a certain concentration. Might be the same for passive transport, I honestly don't know. Perhaps increased flow rate would alter that amount given an increased exposure, which would go along with why plants can survive in very low nutrient rivers.

    All of this would probably explain why I've never had nitrates go below about 5ppm (roughly given the test kit) despite other nutrients being present.

    -Philosophos
     
  3. abcemorse

    abcemorse Prolific Poster

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    That's kind of what I was thinking, but I also wonder if concentration differences would drive the rate to some degree, as substances flow from levels of higher concentration to areas of lower concentration. Just kind of thinking out loud.......
     
  4. Tom Barr

    Tom Barr Founder
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  5. abcemorse

    abcemorse Prolific Poster

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    Perfect! Will read, thanks!
     
  6. Tom Barr

    Tom Barr Founder
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    The 1/2 constants can change depending on species. The K 1/2 constants are what tells you how fast a species will take up based on the concentration. The lower the K1/2, the better they can compete at lower nutrient levels.

    Plants have about 10-100X high K1/2 than epiphytic algae.
    100-1000x for phytoplankton vs plants.

    That's just one reason that algae do not compete with plants for nutrients, their nutrient demands are so vastly different. Nit wits heave and hoe over this topic daily on line without ever bothering to look any of this stuff up to see if they are right, even worse.....they poo poo anyone even when they point out the basic idea and topic with references, all in some effort to poo poo EI and excess nutrients:cool: Then they got the nerve to call their whacked idea/s "Science" because they used a Nitrate test kit.

    Regards,
    Tom Barr
     
  7. Philosophos

    Philosophos Lifetime Charter Member
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    Hey now not all of us who have 3-4 semi-reliable test kits are so bad :p I happen to love second or third rate NO3 tests only because P and K are even more of a pain.

    Anyhow, where do we go for a full and strait forward profile of nutrient demands for algae? You've spent a ton of time researching, and I'm sure most of us would appreciate a dumbed down version as to why and how algae function differently. In the past you've always emphasized good plant growth to push out algae competition, but now you're talking about the differences in nutrients. This concept is something we haven't seen a whole lot of, besides some obvious speculation with calcium and co2. How does it work?

    -Philosophos
     
  8. Tom Barr

    Tom Barr Founder
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    1. Scale, algae have a far far higher surface to area(SA) ratio than any plant.

    A)
    This means they have far surface relative to their biomass to take up nutrients. So they can scavenge for trace amounts very effectively.

    B) As far as scale, a single to multi cell little algae, with a few micrograms of dry weight at most compared to a plant, maybe 1000-100000X more biomass is somehow going to be able to survive on less nutrients than the algae is silly.

    Plants also have lots of other structures, support, architectures that require much more carbon than algae. It only takes a 1000% less biomass of algae to ruin a planted tank's look with an alga bloom.

    It's like feeding livestock: trying to stave mice to fed your elephants.

    If you look at Carbon, N, P requirements for algae limitations, chemostat studies, they are quite low. Algae are well studied, aquatic plants much less so. Still, we can see and infer much based on size alone(that does not change as many larger algae are plant sized).

    Regards,
    Tom Barr
     
  9. abcemorse

    abcemorse Prolific Poster

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    Excellent article. Never done SW but now I know why calcium is added, serves the same purpose as CO2 in planted tanks, cool. It is still very interesting how we can provide everything algae needs (same stuff as plants) in copious quantities and fend off algae. The combination of nutrients, light and CO2 must be just enough out of the comfort zone for algae to ever get a good foothold...hopefully it won't evolve to better utilize our conditions. I guess at that point we change them again:rolleyes:
     
  10. nipat

    nipat Guru Class Expert

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    If I get it right, I think Tom's concept in algae control is mainly to prevent the spore
    from germination as much as possible by limiting NH4, stable CO2 supply, low light, etc.,
    then use black out or Excel to get rid of the existing one, depending on species.
     
  11. Tom Barr

    Tom Barr Founder
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    Yes, they are not just a function of nutrients, CO2 and light supply alone.
    That is what many seem to assume, and if that was really the case, every aquarium would have issues that had any light..........

    We just do not see that, so it cannot be nutrient supply or CO2.....light plays a strong role with algae.

    Has to be some other issue.
    Some algae might be induced via some spores from another tank, say Spiroghyra or Cladophora and then slowly grow, fragment and then appear to take over suddenly. These algae act more like mosses, and other plants. Some like GW, need more than just plant ferts, CO2 and light. When the plants are growing well, in sufficient biomass relative to the water volume, they define and dominate the system.

    Regards,
    Tom Barr
     
  12. abcemorse

    abcemorse Prolific Poster

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    It seems too, at least in my tank, that BBA likes to attack plants stressed not from nutrient/light/CO2 issues but damage as well. The only places it really shows up at all is on the edges of angelfish-chewed leaves that are struggling and the cut off leaves of dwarf sag (which I have since quit cutting like that......)
     
  13. abcemorse

    abcemorse Prolific Poster

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    This is good stuff. So, I'm assuming that the generally agreed upon 20-40 ppm NO3, 1-2 ppm PO4, etc, etc are concentrations somewhat to well above (depending on species) the Vmax for most species kept in aquaria. Are there any other substances outside of CO2 that you know of that can increase a plant's active transport capabilities and not be harmful to fish? (assuming here that I read the article correctly by understanding that the cell concentrations of most nutrients are several orders of magnitude higher than the water column, effectively negating passive, diffusion type uptake). If so, would that tend to discourage algae growth even further?
     
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