O2 current and growth

[Tom Barr]

Paper I recently read on O2 inside Egeria densa and the effects of current was interesting.

As expected, the partial internal pressure of O2 in the root and the shoot was lower in moving water vs static. O2 did not increase till about 1 hour after illumination. Then it was steady and increased to 300% as kPa after about 7 hours in static systems, but only about 60% increase in moving systems and peaked around 6 hours for the shoots.

The roots where similar however and bit higher for moving water.
They increased about 150-200% when illuminated.

This means there is a lot of O2 being pumped into the sediment regardless of current. In the water, the current reduces the O2 internally, so less pearling occurs and this may have some effects on better growth.

With lower internal O2, CO2 is easier to fix since O2 competes with CO2 for fixation with Rubisco.
So less photorespiration may occur, resulting in better more efficient growth and more export of O2 into the water.

All good things.
The roots are unaffected so the bacteria and cycling in the sediments are unchanged.

Aquatic Botany, Sorrell and Dromgoogle, 1987


Regards,
Tom Barr

 

[dbazuin]

So does this means that the air bubble's sometimes appear from the substrate near plants is O2 and not the result of the substrate is rotting.

 

[CL_]

Tom, would you think that the higher O2 pressure inside plants in stagnant water would be because there is an "orb" of sorts of water saturated with O2, so hardly any more O2 can be absorbed into the water from the plant, where as current would be blowing water that isn't saturated with O2 around the plants, so more O2 can be dissolved? (similar to how water evaporates faster when air is blown on it, not only because the ripples increase the surface area of the water, but also because there isn't an "orb" of high humidity air)

 

[dutchy]

So does this means that the air bubble's sometimes appear from the substrate near plants is O2 and not the result of the substrate is rotting.

I definately believe so. I can see bubbles come out of the substrate by the end of the photoperiod, especially where the L. Aromatica grows. If the substrate would be rotting I think this would be a continious process, not depending on light. In the substrate it's always dark. Of course this is just my attempt to logic reasoning and observation, I don't have any authorotive sources to back it up.

regards,
dutchy

 

[dbazuin]

dutchy,

Thats true it starts always at the same time pearling start.
Not that I see much pearling now I have increased the flow.

Greetings Dirk

 

[Tom Barr]

Tom, would you think that the higher O2 pressure inside plants in stagnant water would be because there is an "orb" of sorts of water saturated with O2, so hardly any more O2 can be absorbed into the water from the plant, where as current would be blowing water that isn't saturated with O2 around the plants, so more O2 can be dissolved? (similar to how water evaporates faster when air is blown on it, not only because the ripples increase the surface area of the water, but also because there isn't an "orb" of high humidity air)

This is a function of Fick's 1st law of diffusion.
Or, more a boundary layer issue, not one of saturation.

http://en.wikipedia.org/wiki/Fick's_laws_of_diffusion

There's less exchange with the boundary layer and the layer is much larger.
So O2 pressure builds up against this boundary layer to form partial pressures of O2.

This also implies more Ethylene and CO2 diffusion as well, which can lead to stem elongation.
I noticed my Blyxa stays and grows shorter in higher current than in other locations.
Other stem plants do also.

Might be something to it.

But yes, more O2 can be dissolved, but more will be degassed also, same for CO2, but as long as we do not cause the surface to break much, a good amount will be retained.

Another idea is to use current like a lighting timer for a noon day burst, then reduce the current back down. At night, raise it back up and so on.
Anytng to maximize the O2 over the entire 24 hour cycle.

Regards,
Tom Barr

 

[Tom Barr]

I definately believe so. I can see bubbles come out of the substrate by the end of the photoperiod, especially where the L. Aromatica grows. If the substrate would be rotting I think this would be a continious process, not depending on light. In the substrate it's always dark. Of course this is just my attempt to logic reasoning and observation, I don't have any authorotive sources to back it up.

regards,
dutchy

Well, as the plants add O2 to thr sediment much more during the light phase, the O2 allows bacteria to cycle much better/faster, this produces more CO2 via respiration.
The gas might be CO2 as well, more likely in fact since there's virtually any current in the sediment relative to the water column.

So the bacteria have a field day when the plant roots are growign well and pumping a lot of O2. This means with stronger plant growth in the shoots(the source of the O2 in plants), there is more available to pump down into the root zone.

I think there is a strong relationship between good root growth/O2/bacteria and aquarium, aquatic plant stability, algae etc.

Regards,
Tom Barr

 

[CL_]

This is a function of Fick's 1st law of diffusion.
Or, more a boundary layer issue, not one of saturation.

http://en.wikipedia.org/wiki/Fick's_laws_of_diffusion

There's less exchange with the boundary layer and the layer is much larger.
So O2 pressure builds up against this boundary layer to form partial pressures of O2.

This also implies more Ethylene and CO2 diffusion as well, which can lead to stem elongation.
I noticed my Blyxa stays and grows shorter in higher current than in other locations.
Other stem plants do also.

Might be something to it.

But yes, more O2 can be dissolved, but more will be degassed also, same for CO2, but as long as we do not cause the surface to break much, a good amount will be retained.

Another idea is to use current like a lighting timer for a noon day burst, then reduce the current back down. At night, raise it back up and so on.
Anytng to maximize the O2 over the entire 24 hour cycle.

Regards,
Tom Barr

So it's not that the plants produce less O2 (would it be safe to say that they might be producing more?), it's that the O2 isn't being trapped in the plants, so we'll see less pearling.
I have noticed that plants pearl a lot when you turn off all of your powerheads, filters, etc. This could explain why I see less pearling in my 48 gallon tank than I did in my 20 gallon tank back in the day with DIY CO2. I now use much more flow.

Makes sense.