Why plants do well if you have good CO2 and light at the start of the light cycle

Tom Barr

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This is speculation but I did measure the parameter O2. So I have 1/2 the equation.
I've been very sick and laid up the last 2 weeks, so sitting there looking at the tanks...........your mind wanders.

I noticed all the pearling going on. Often rather large bubbles and mostly where the more established root systems are present.
I waited and watched the bubbles over several hours and several days. I watches WHERE the bubbles where coming from.
Most actually where coming from the sediments and root zones from well established root zones.

This gas is not O2. Since the sediment is rather shallow, there's really only one gas it can be: CO2.
As bacteria, microinvertebrates and roots respire, they give off a lot of CO2. Roots pipe the O2 into the deeper areas of the sediment if the plant has ample light and CO2.

The sooner that process starts, the sooner the pearling of CO2 also starts, as well as the O2 in the water and on the leaves.
So it's a synergistic effect, good CO2 and light from the start of the day= good CO2 and even more O2 so the roots and other heterotrophes can respire even more CO2.
I accidently hit the output of the CO2 regulator when I removed a gas tank. It went from 10 psi down to about 6psi. I noticed the tank did not pearl much at the start, and smaller tip growth in the faster growing species. CO2. I looked, and spotted the gauge, adjusted back to 10 psi.
Good growth and pearling like described above returned. O2 dropped also, about 1 ppm, which is a lot for a planted tank during that time. Obviously the CO2 dropped also, but the feedback loop from more healthy growing plants pumping more O2 into the sediment, that then in turn.............produces more CO2 for the tank...........

Seems that the CO2 produced by the sediment (from plant roots) is relatively important. I think this is one of the main drivers of good growth in non CO2 and also CO2 enriched systems.
It also likely is a large factor with algae control also, algae do not have roots, so where there are not roots or much around/growing poorly, the algae will do well.

That would explain a lot of the observations for both non CO2 and CO2 enriched plant dominance.
We always hear how healthy plants = no algae, but the roots and O2 piping and then CO2 production might be the link.
With well established root systems, topping might provide a better option to avoid algae.
 

oliverpool

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Hi Tom,

I do notice this big bubble coming up every once in a while from I believe the soil where my ranunculus resides. As they are one of the plants that is really growing super well in my tank and at times threatening to take over the tank with their numerous runners. The location of the bubbles basicaly near where the rannuculus is and your theory of the deep roots seems to make sense. Just that I do not understand why it would be co2 instead of o2 as my sediment is rather deep in my case?

Hope you are better now.
 

oliverpool

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Hi Tom,

I do notice this big bubble coming up every once in a while in my tank. I believe its near the soil where my ranunculus resides. They are one of the plants that is really growing super well in my tank and at times threatening to take over the tank with their numerous runners. The location of the bubbles near where the rannuculus is and your theory of the deep roots seems to make sense. Just that I do not understand why it would be co2 instead of o2 as my sediment is rather deep in my case?

In my tank I do not get alot of pearling. The pearling or small pearling only seems to happen on the slow growing plants like my buce and annubias.

Hope you are better now.
 

Tom Barr

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Plants give off O2 in the shoot/leaves etc, above ground parts, not the root zone. The roots do not produce O2, but O2 is sent down to the root zone when it builds up inside the aerenchymenous lacunae. It is quickly used by bacteria and the roots. Then the waste is CO2.
You can measure and see the O2 levels as a function of redox dirually with the light cycle in the sediment, but virtually none will expelled as O2 from the root zone. And certainly not all those larger bubbles.


The O2 on leaves helps dislodge algae and the faster growth quickly shades and buries the algae. It takes time for algae to attach and grow. Faster growth of plants= less time for algae to get established.
But, less light= less plant and algae growth.
 

UDGags

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So would one get the same effect if they plumb/pipe oxygen (air mixture most likely) into the sediment? The bacteria would output more CO2, which in return can be used by plants.

Off this same logic....Can one buy this bacteria? I'm thinking a fluidized bed type reactor in-line with plumbing (similar to a cerges) where you input air (oxygen) and you get out CO2.
 
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aamir9110

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root activity

Tom, wish you a speedy full recovery.

I have also noted this a lot now that i am trying to optimize CO2 levels as the lights come on. Plants just look fuller and there are many BIG bubbles popping out of the root zones in a cluster of S.repens.

Regards,
AR
 

Tom Barr

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UDGags;120245 said:
So would one get the same effect if they plumb/pipe oxygen (air mixture most likely) into the sediment? The bacteria would output more CO2, which in return can be used by plants.

Off this same logic....Can one buy this bacteria? I'm thinking a fluidized bed type reactor in-line with plumbing (similar to a cerges) where you input air (oxygen) and you get out CO2.

Yes and this would be a good experimental treatment method to try and see.
You do not want a FBF flow rate, you only need a very slow steady flow of O2 coming in.

Much like the RFUG's I'd used with CPVC 1/2" tubing and copied from the Excelon style UG filters(they used 3/8") from the 1960-1970's.

You'd need to slowly add O2 enriched water.
The flow rates I used in past were pretty high. In this case, we would be adding a lot more O2 than is in the water column typically.
But at a slow rate so not much would ever end up in the water column above.

So instead of a powerhead driving the RFUG, you'd use say a dosing pump with 1 ml per min over say 4 sqft and only during the light cycle.
We already know what the optimal flow through rate is for roots, roughly .49 liters per meter squared per day.
But that's flow, not O2.

Still at 1.1 mls /min, that's about 8 hours for a meter squared area for that dosing pump over 8 hours lighting cycle.
A m^2 is about 1550 sq inches.
My 120 gal is about 1440 sq inches.

I think an O2 reactor and a recirculator would work, like the Kalk and Ca reactors using the dosing pump.
 

Tom Barr

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aamir9110;120248 said:
Tom, wish you a speedy full recovery.

I have also noted this a lot now that i am trying to optimize CO2 levels as the lights come on. Plants just look fuller and there are many BIG bubbles popping out of the root zones in a cluster of S.repens.

Regards,
AR

We see this a lot more with plants that have the larger lacunea and more aggressive root systems.
Starougyne certainly has many traits that Crypts and Swords do.
Many stem plants have thinner delicate roots, but overtime, those can still develop into mighty pipe systems.

I think algae links to this cycling. With all the O2 produced and light shading by plants, most of NH4 gets taken up by plants or bacteria, and there's ample CO2 for plants when light 1st hits the leaves that's present in the water, then that is used to drove more production of O2, which in turn drives more uptake of CO2.
It's important to note that plants get the O2 from H2O, not CO2.

But the cycling between the plants, the water and the bacteria in the sediment seems like a a good feedback loop and one that would stabilize things in aquatic systems.
New tanks have trouble perhaps because the sediment is not matured yet.

If you have a good filter and old sediment, redoing the tank does not pose any set back I've noted a few times.
I still do more water changes for a month or two, but the tank's always bounce back real well vs a brand new tank, sediment and filter.
Few would disagree with that comment.

Still, it says something is important about the roots and bacteria/microinverts, that we tend to ignore or not deem that important.
We are not really interested in growing roots, mostly the tops and shoots we see.
Plants get algae on older leaves when you replant them. Once the roots and bacteria re establish, the old leaves are trimmed off and the new leaves do not get any algae.

Thus there are several observations that offer support for this hypothesis.
We really do not know why plants dominate in many systems, nutrients alone does not explain the patterns.
Nor does light. CO2? Perhaps.
Bacteria and CO2 and O2?

I think that's a more complex system, but more likely to be the case.