Interesting question during the oral exam about CO2 and reactive oxygen species(ROS)

Tom Barr

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I had an interesting query: what would occur to a submersed aquatic weed if there was a sudden decline in CO2 under high light/non limiting nutrients?

What would happen in the Light reactions?
There would be a back up of NADPH, ATP and lots and lots of high energy electrons, which can over load the light reactions causign the formation of reactive oxygen radicals.

These ROS's in turn destroy the very enzymes that are suppose to gather light energy and feed it into the light reactions to send to the dark reactions where the CO2 is fixed.

By decoupling these light and dark reactions..........this causes a severe back up of incoming light energy => biochemical reactions begin to back up=> these expose the enzymes more and more to ROS's which attack and destroy the enzymes required for photosynthesis.

http://www.biosensitivefutures.org.au/overviews/principles/images2/photosynthesis.gif

See the part that splits the water?
See the electron carriers and the PQ- and PQ?
There's a few others, but all these are overloaded with electrons.........they have to go somewhere, so a few start attacking the D1 enzyme that splits the water into O2 and e-.

Plants can regulate this balance somewhat under optimal conditions, but if the temp goes way up, say 40C, or the CO2 is suddenly gone.........or some other stresses.........then this ROs effect occurs and can be intense.

Since there is little CO2, there's little food for plants.
Plants can adapt to some degree, but this takes time and sudden large CO2 changes seems to really cause a lot of issues within submersed plants that are simply not present with terrestrial species.

We enrich the CO2 so this difference is even larger in many cases. Going up higher in CO2 seems okay, but not dropping or bobbing between high and low.

I passed BTW(the exam).

Regards,
Tom Barr
 

Biollante

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Never A Doubt

Hi,

Never a doubt. Congratulation on passing your exam! :)

Nice diagram, thank you.

Without pretending I understood this, I think this is central to understanding the condition we observe when we get CO2 bouncing around or make sudden changes in lighting.

I suspect it is at least analogous (though different mechanisms) to other large changes we make to the systems (aquariums) that weaken the system and provide nutrients (encouragement) for algal growth.

Biollante
 

Tom Barr

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Another way to think about, while a bit extreme........it's like removing the lightning rod from the house and having it get struck.

Instead of sending the electrons where they are suppose to go(the ground), the energy rips through the house destroying things on it's way.

At the cellular level, this is sort of what happens if there's a sudden back up in the energy.
Plants have some protection systems, but these are/can be overloaded.

Regards,
Tom Barr
 

Tug

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Is this a problem when bobbing between concentrations of nutrients/CO2 at levels that could be considered non-limiting amounts? For example, bobbing between 30ppm and 40ppm of CO2 would be better then bobbing between 15ppm and 25ppm. Of course, stability would seam to be the best solution overall.

"I want to take you higher"
 

Tug

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Could it be that these enzymes are evacuated by the plant cells and picked up by algae spores?
 

Tom Barr

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Tug;50693 said:
Is this a problem when bobbing between concentrations of nutrients/CO2 at levels that could be considered non-limiting amounts? For example, bobbing between 30ppm and 40ppm of CO2 would be better then bobbing between 15ppm and 25ppm. Of course, stability would seam to be the best solution overall.

"I want to take you higher"

I doubt there's much issue if there's a non limiting level, non limiting is by it's very definition, non limiting to growth.
Problems arise when folks assume they have non limiting CO2, when they very well may not.
Hell, that gets me time to time, even the top scapers in the world will get nails on this one time to time.

Less observant folks?
Very likely.
DIY?
Same thing, maybe worse.


Regards,
Tom Barr
 

Tom Barr

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Tug;50695 said:
Could it be that these enzymes are evacuated by the plant cells and picked up by algae spores?

No, proteases chop them up or the cell dies and the enzmyes are already destoyed leak up. Bacteria attack, then perhaps the basic N groups can be used.
There might be a signalthat leakign stressed plants give off, or perhaps the sudden change itself is a factor in algae.

But.......as far as plants..........this is what occurs, algae tend to do well at higher light.

If there's enough growth, algae will roast themselves with O2, 200-300% etc.......toxic O2 levels.

Regards,
Tom Barr
 

Biollante

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Periphyton Bloom?

Tom Barr;50689 said:
Another way to think about, while a bit extreme........it's like removing the lightning rod from the house and having it get struck.

Instead of sending the electrons where they are suppose to go(the ground), the energy rips through the house destroying things on it's way.

At the cellular level, this is sort of what happens if there's a sudden back up in the energy.
Plants have some protection systems, but these are/can be overloaded.

Regards,
Tom Barr

Hi,

It would seem that this is an invitation to Periphyton bloom (if that is the right word). The complex little community out of balance would likely favor one group in that community over others, specifically I am thinking of the cyanobacteria component. But really whoever can most efficiently channel the energy and consume the nutrients (waste produced).

Biollante
 

Philosophos

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This thread and that chart are going right into my bookmarks. This is another one of those things we should all know at least the basics of, but most don't.

It's incredible how many people give up on plants without taking account that the ones they buy from the store are high light/tons of compressed CO2 and they're sending them off into CO2 limiting environments. I've had it happen with my own plants that I've given to others.
 

Tug

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They each have their down side. More can go wrong with yeast for less observant folks. On the other hand yeast will give you only so much CO2. A less observant person (someone who works for a living) could very easily gas their fish with pressurized systems.

With a yeast reactor most of my focus is on keeping the fermentation from sticking, improving the water flow and adjusting the lighting. Now that I'm close to providing non limiting levels of CO2 I do see some pearling after a water change. I can conjecture that I am close to providing the right amount of CO2, keeping the enzymes from being destroyed completely, but just short of the mark due to flow issues I have yet to address.

Tom Barr said:
Less observant folks?
Very likely.
DIY?
Same thing, maybe worse.
 
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Tug

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Roasted algae on an open fire, Batman! Toxic O2 levels? Is this some kind of a trick answer?
Tom Barr said:
If there's enough growth, algae will roast themselves with O2, 200-300% etc.......toxic O2 levels.
 

Biollante

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Vitamin C Anyone?

Hi,

The reactive oxygen species (ROS) that started this discussion really is no different from folks using hydrogen peroxide to kill cyanobacyeria. For that matter, other attempts to raise ORP values to improve water quality. I do not know if the term “free radicals” apply, but it seems that is what we are fighting.

People take vitamin C for the “antioxidant” to fight damage of ROS, deal with those “free radicals.”.

I believe, not sure, that when people talk about “cellular signaling” ROS is the method. I think “signaling” is mainly redox or oxidative signaling.

It seems odd that when adding sodium percarbonate to the water column, the first thing we see is a significant reduction (scary) in ORP value. To a lesser intellect as me, this seems counter-intuitive.

Biollante
 

Tom Barr

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Tug;50798 said:
Roasted algae on an open fire, Batman! Toxic O2 levels? Is this some kind of a trick answer?

Under high growth conditions, algae will over produce O2.
Plants are less likely to do this. They tend to be limited by CO2, and floating plant leaves are immune.

Regards,
Tom Barr
 

Biollante

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Cool!

Hi,

So this condition of limited CO2 in aquatic plants is rather equivalent to Achim Trebst’s work showing that impeding the electron flow through electron transport chain of photosynthetic apparatus is a source of real problems for green plants generally.

That Hoffman, et al in 2005 built on to demonstrate Arabidopsis thaliana, Mouse-ear cress, that heat and water deficiency causing closure of the stomata which in turn triggers lower CO2 in the leaf therefore less photosynthetic production that leads to “indirect” damage caused by the production of free radicals, reactive oxygen species (ROS).

Of course, in aquatic plants the CO2 deficiency is not caused by stomata closure but by lack of available dissolved CO2, which is why floating plants are not affected. It also answers one of my questions about signaling. :)

I may not be very smart but this is cool, that was an interesting question, even if it took a while for me to catch on, thanks. :D

Biollante
 

Tom Barr

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DaBub;50923 said:
Is peroxide a result of ROS?

Or element of it?

H2O2 is produced inside the plant, algae cell.
A certain amount is awlays produced.
Plants, algae use catalase to detoxify it, super oxide is even more damaging, SOD enzyme takes care of most of this.
It's only when there's a sudden jump or problem with CO2 supply that these can back up, or some decoupling in this biochemical pathway that problems arise.

Once permanent dmanage is done, it can take a long time to repair, often easier for a plant to simply make a new cell, leaf etc than to reapir the old one.
This is much different than external H2O2 additions, or exogenous ROS.

Regards,
Tom Barr
 

DaBub

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Thanks, I am not sure I get it

maybe it is sinking in

It is an enzyme that limits the peroxide that would be Peroxidases.

Does the external use of H2O2 overwhelm the Peroxidases? Or it is seperate unrelated event?
 

DaBub

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The SOD enzyme went right by me...

sorry missed it.

Like a broken pipe, until it is fixed or replaced, the losses continue.
 
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Tug

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I feel like the guy that hails a cab only to watch another person get to the cab first and take off without me.