CO2, leaf morphology and uptake relative to current

[Tom Barr]

Wiley InterScience :: Session Cookies

Regards,
Tom Barr

 

[ceg4048]

Tom,
A fascinating read this one. I'm surprised that the laminar flow max CO2 absorption limit inboard from the edges is so low though. 0.5-3 cm/sec is only about 0.1-0.6 mph which is far lower lower than the optima values some of the other experiments mentioned. I recall 1-2 mph being the reported upper limit for max absorption.

So this suggests that pummelling the leaves with high flow is counter-productive and may be less effective than we think, except that there is always the issue of leaf blocking and orientation.

One interesting bombshell comes at the end though where he theorizes that apart from a boundary layer thickness increase due to turbulent flow at higher Reynold's numbers, one of the effect of higher velocity is a disruption of the protons pumped from the cytoplasm thereby affecting HCO3 assimilation. This is a bit murky and I was hoping you could clarify.

The author makes an allusion to (for plants that utilize HCO3) "...extracellular carbonic anhydrase-mediated conversion of HCO3 to CO2 requires H+ that is pumped from the cytoplasm to the extracellular medium through plasma membrane bound ion channels..." (pg 1338)

From that description I'm surmising the origin of these H+ is the proton translocation of the Electron Transport Chain that powers the chloroplast's ATP Synthase complex. If that's the case is the inhibitory effect to photosynthesis a result of lower ATP production via reduction of the proton gradient across the bi-lipid layer?

He then appears to imply that for plants which don't feed on water column HCO3, internally convert CO2 to HCO3 in order to generate a higher CO2 gradient across the membrane to garner more CO2. He appears to be say that mechanical stretching of the plasma membrane by the impact of high flow for these types of planes allows the sequestered intracellular HCO3 to escape and be lost across the membrane. Is this a correct interpretation and if so do you agree with that assessment?

What is the mechanism of CO2=>HCO3 conversion, i.e. is it enzymatic? If so which enzyme?

Can we assume that boundary layer thickening due to non-laminar flow also affects the other nutrient transfer across the layer as well? If so can you confirm that higher CO2 injection rates and higher dosing levels can mitigate these effects?

Is there any general tell-tale signs from leaf morphology that indicates whether the plant is a HCO3 user or strict CO2 feeder? I've never seen a list which segregates according to this type, although Vallis seems to be known as an HCO3 feeder.

Could there also be a correlation between the "difficulty" of plants and their ability (or lack thereof) to utilize HCO3?

Would appreciate any thoughts.

Cheers,

 

[Tom Barr]

The bicarb uptake is where the flow messes things up.
The H+'s come out the bottom of the leaf, coverts the HCO3 to CO2 via pH change, the leaf takes it up. This is called indirect bicarb use. Other plants/algae use direct bicarb use, they actively use HCO3, kick off the OH, and take in the CO2.
The OH rises pH often to about 10 or higher. Algae and some plants make specific deposits to make their CaCO3 precipitate formations.

At high current, this means it gets tosses away from the leaf and wasted.
No CO2.

If we add CO2, this is not an issue.
If we use CO2 mist, then neither is an issue, the mist disrupts this boundary layer quite well I'd imagine.

The common enzymes: Carbonic anhydrasae(CA) and PEP carboxlyase(PEP)(C4 plants etc). We have CA as well for our blood and balancing the ratio of CO2 to HCO3.

Carbonic anhydrase - Wikipedia, the free encyclopedia
Most aquatic plants and algae have carbon concentrating mechanisms as well, this means more cO2, less O2 around Rubsico, so it runs better. Also, with carbon fixation, you get a lot more/better results when N is not limited.

This is why EI dosing can drive much higher rates of CO2 fixation than say more limiting methods. Some claim this is the way/path to reduce the rates of growth and reduce the CO2 demand, hogwash, use less light and you get that and more wiggle room. Much easier, less work, less waste and less algae growth as well.

Here's another reference:
ChemPort Reference Linking Service

You should realize something though..............why do all this to get CO2, unless it is limiting growth in the first place?
It's neat etc, but does not apply to us unless we are limiting CO2.
Since we are not trying to do that, no one this is done

More in book form:
Plant Physiological Ecology - Google Book Search

Regards,
Tom Barr

 

[Tom Barr]

Can we assume that boundary layer thickening due to non-laminar flow also affects the other nutrient transfer across the layer as well? If so can you confirm that higher CO2 injection rates and higher dosing levels can mitigate these effects?

Well, CO2 is by far the most limiting effects of growth on plants, but you can gte N and PO4 limitation which reduce the effects of CO2 demand.

Still, the real issue here is CO2 limitation.
This is where it's all at.

You get much smaller effects with PO4 and NO3.
Nothing gives effects like cO2.

Is there any general tell-tale signs from leaf morphology that indicates whether the plant is a HCO3 user or strict CO2 feeder? I've never seen a list which segregates according to this type, although Vallis seems to be known as an HCO3 feeder.

Could there also be a correlation between the "difficulty" of plants and their ability (or lack thereof) to utilize HCO3?

Would appreciate any thoughts.

Cheers,

Hard to say, but some have been researched and shown to be strict CO2 users, but in the same genus, there are plants that use CO2 and bicarb.

See the references above.
CO2 limitations also appear as progressively smaller new growth, stunting tips, algae of course.............this is true for CO2 bicarb users as well, but they are less affected and really beat up on the CO2 only users.


Regards,
Tom Barr

 

[ceg4048]

If we add CO2, this is not an issue.
If we use CO2 mist, then neither is an issue, the mist disrupts this boundary layer quite well I'd imagine.


You should realize something though..............why do all this to get CO2, unless it is limiting growth in the first place?
It's neat etc, but does not apply to us unless we are limiting CO2.

Since we are not trying to do that, no one this is done

Thanks, it's a bit clearer now. The thing is though that it really is an issue even though we are adding CO2. A lot of people will simply point a pump outlet directly at a bed of plants and the that bed will develop BBA or some other CO2 stress related injury. That becomes a real head scratcher and so I'm suspecting that it's due to this phenomenon. Clearly, many claim a green dropchecker while experiencing BBA and we'll often respond by suggesting to add either more CO2 or more flow. I'm just wondering whether there is any need to temper our inclination to just assume throwing more flow at the problem should fix it. See what I'm getting at?

The chemport link article confirms the origin of the protons is from the light dependent complexes but this confuses me. Aren't these complexes on the upper side in the palisade region??? How are protons moved from this area to the abaxial side while OH expulsion occurs on the side generating the protons? Could you clarify please?

Also, although intuitive, it's not exactly obvious by what mechanism unlimited N helps in this. N doesn't appear in the CA equation nor in the Rubisco equation. Is is simply due to high chloroplast production in general or is there a more specific role in N's ability to garner higher intracellular CO2 concentrations?

Thanks,

 

[VaughnH]

This is possibly nit picking, but in aerodynamics higher Reynolds Numbers give thinner boundary layers, not thicker. And laminar flow gives the thickest boundary layers. I'm not sure if liquid flow acts that way, but I know supersonic gas flow, which is incompressible flow, does, having spent several years working with aerodynamics and gas flow.

 

[JDowns]

Also, although intuitive, it's not exactly obvious by what mechanism unlimited N helps in this. N doesn't appear in the CA equation nor in the Rubisco equation. Is is simply due to high chloroplast production in general or is there a more specific role in N's ability to garner higher intracellular CO2 concentrations?

Thanks,

Tom pointed me to this article awhile back which may be usefull here. I'm still trying to wrap my head around it completely but things are getting clearer.

If this article shouldn't be linked in this manner please advise. I saved it because it moved and old links wouldn't point to it any longer.

The interaction between elevated carbon dioxide and nitrogen
nutrition: the physiological and molecular background

 

[ceg4048]

This is possibly nit picking, but in aerodynamics higher Reynolds Numbers give thinner boundary layers, not thicker. And laminar flow gives the thickest boundary layers. I'm not sure if liquid flow acts that way, but I know supersonic gas flow, which is incompressible flow, does, having spent several years working with aerodynamics and gas flow.

Within the laminar flow regime, increasing Reynolds number reduces the effective boundary layer thickness. As long as there is no flow separation the flow follows the contours of the surface. The author of that article indicates that when the flow transitions from laminar to turbulent flow the effective boundary layer thickness increases in comparison to what it was before the transition. Thickness increases as it fails to follow all contours (in effect skips across) and then starts to decrease as the Reynolds number increases. It is the transition region of flow that the article discusses. The other issue is that the thickness increases as the distance along the path increases.

JDowns, thanks for the link . It works perfectly and I was able to add that article to my collection. That article more or less discusses N uptake in response to elevated CO2 levels though, which is the opposite of my question of how elevated N levels affect CO2 uptake. What I did note however is that paragraph 2.7discusses NO3 conversion through a series of reductase enzymes in order to produce Glutamate ultimately used in the production of amino acids. I can only assume that higher N produces high amino which directly affects Rubisco production which then affects carbon fixation. I'm unsure whether that's in fact what Tom had in mind but it seem reasonable.

Cheers,

 

[VaughnH]

Within the laminar flow regime, increasing Reynolds number reduces the effective boundary layer thickness. As long as there is no flow separation the flow follows the contours of the surface. The author of that article indicates that when the flow transitions from laminar to turbulent flow the effective boundary layer thickness increases in comparison to what it was before the transition. Thickness increases as it fails to follow all contours (in effect skips across) and then starts to decrease as the Reynolds number increases. It is the transition region of flow that the article discusses. The other issue is that the thickness increases as the distance along the path increases.

Cheers,

Thank you. That makes sense now. In aerodynamics you described separated flow more so than turbulent flow, but when I was working in that field we did nothing at all with the transition flow, and very little with laminar flow, for that matter.