Flourish Excel Question? - The Planted Tank Forum
 
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post #1 of 5 (permalink) Old 09-21-2011, 02:59 PM Thread Starter
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Flourish Excel Question?

Hello planted tankers. I was hoping that someone here understood the chemistry behind why Excel works and what exactly it does well enough to explain it to me. I can see that it does work; my plants are doing obviously much better now than they were without it, but I am interested in the why and how of it. If anyone could clear this up for me my curiousness greatly thanks you.

I even have duckweed in my water bong!
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post #2 of 5 (permalink) Old 09-21-2011, 03:52 PM
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Most folks think the likely explanation is that the toxic glutaraldehyde enters plant cells and is broken down by a protective enzyme, producing glutaric acid. Plants may be able to increase their production of this enzyme if needed, as evidenced by partial adaptation of some sensitive plants (like anacharis) to gradually increasing levels.

Then the glutaric acid is further metabolized to produce CO2, which then gets processed in the normal way. The entire process occurs within the plant tissue, rather than the tank water, which is why Excel doesn't increase measurable CO2 levels.

Others think that because glutaraldehyde bears some similarity to intermediate chemicals in the long photosynthetic process, it can be substituted in at some point, effectively shortcutting the normal process.

Seachem itself has a brief on it, and claim that it would take studies using radioactive carbon tracers to determine which explanation is right (maybe both).

That's the simplified explanation. I've seen others go into details which are incomprehensible to me.
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post #3 of 5 (permalink) Old 09-21-2011, 04:31 PM Thread Starter
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Originally Posted by DarkCobra View Post
Most folks think the likely explanation is that the toxic glutaraldehyde enters plant cells and is broken down by a protective enzyme, producing glutaric acid. Plants may be able to increase their production of this enzyme if needed, as evidenced by partial adaptation of some sensitive plants (like anacharis) to gradually increasing levels.

Then the glutaric acid is further metabolized to produce CO2, which then gets processed in the normal way. The entire process occurs within the plant tissue, rather than the tank water, which is why Excel doesn't increase measurable CO2 levels.

Others think that because glutaraldehyde bears some similarity to intermediate chemicals in the long photosynthetic process, it can be substituted in at some point, effectively shortcutting the normal process.

Seachem itself has a brief on it, and claim that it would take studies using radioactive carbon tracers to determine which explanation is right (maybe both).

That's the simplified explanation. I've seen others go into details which are incomprehensible to me.
Thanks for the explanation and the link; both were helpful to me. To make sure I understand, let me paraphrase this. Basically, what Excel does is provide available carbon in the form of extremely simple sugars that can take the place of the elemental carbon in CO2 and acts as sort of a jumpstarter for initiating the chemical reactions of photosynthesis. Is this correct? If it is, then it brings up another question: how exactly do the simple sugars get into the plant? If I understand correctly, the size of the sugar molecules are quite a bit larger than the CO2 molecules, so where and how do the plants absorb them? (Most of these sugars have 5 carbon molecules plus assorted hydrogen, oxygen and others, while CO2 is much more simple...) If my understanding is off, please correct me. I am very interested in the chemistry of how this works. Thanks!

I even have duckweed in my water bong!
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post #4 of 5 (permalink) Old 09-21-2011, 09:42 PM
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Yes, up-conversion into simple sugars is one possibility; with down-conversion to CO2 being the other.

Glutaraldehyde, according to Seachem, adsorbs into plant cells readily. Once inside the plant, anything it's converted to is also already inside the plant.

The ability of a substance to penetrate into living material isn't related to molecular size alone. As an example, consider dimethyl sulfoxide. It's molecular size isn't much different than any other common solvent; yet it penetrates so anomalously fast that you can put some anywhere on your skin, and less than a minute later taste it in your mouth (resembles garlic).

Afraid I can't provide any more detailed explanation than that. My chemistry knowledge is limited to what curiosity and necessity requires.
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post #5 of 5 (permalink) Old 09-21-2011, 10:44 PM Thread Starter
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Originally Posted by DarkCobra View Post
Yes, up-conversion into simple sugars is one possibility; with down-conversion to CO2 being the other.

Glutaraldehyde, according to Seachem, adsorbs into plant cells readily. Once inside the plant, anything it's converted to is also already inside the plant.

The ability of a substance to penetrate into living material isn't related to molecular size alone. As an example, consider dimethyl sulfoxide. It's molecular size isn't much different than any other common solvent; yet it penetrates so anomalously fast that you can put some anywhere on your skin, and less than a minute later taste it in your mouth (resembles garlic).

Afraid I can't provide any more detailed explanation than that. My chemistry knowledge is limited to what curiosity and necessity requires.
Thanks for your response. I agree that DMSO is a peculiar molecule. It has the properties of a high-penetrating agent (like ketone-based solvents) but acts as a carrier for other molecules through permeable barriers like cellular membranes. One of my undergrad degrees is in pre-professional biology, and I had a chemistry prof that did a series of lectures on DMSO, and even back then I though it was very peculiar stuff. I am actually going to look for my old notes from that class now that I have been reminded of it. But I digress.

I googled glutaraldehyde to see what I could learn about it, and that is a weird molecule too. Used for a bunch of stuff, apparently, including sterilizing medical equipment and water treatment among other things. Several articles actually noted its' use as a fertilizer for aquatic plants, but none of the articles actually had any hard scientific evidence that supported claims of its' viability in providing organically available carbon. All of the articles have something phrased like this: "It is claimed that..." and then the outline of the info provided in the Seachem blurb without actually having anything from a peer-reviewed journal to back it up. There was a ton of stuff though that discussed the hazards of it, most of it from either governmental regulatory agencies or reputable sources that discuss industrial pollutants. Apparently in higher concentrations it can be extremely toxic. Who knew?

I think I will continue to look into it a bit more. Thanks again for your response and the information you provided. Honestly, your explanation is a lot better than any other that I have read so far, so I am inclined to just go with that. My curiousity often gets the better of me, and a little knowledge can be a dangerous thing in my case, but it has been so long since those college chemistry classes that I think stuff like this is good because it keeps me sharp. Just don't ask me to do any stoichiometry. I guess the bottom line is that it works. I can definitely say that my plants are doing far better with it than without. That is the important thing, right?

I even have duckweed in my water bong!
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