# Nutrients, nutrients, nutrients ... does the plant "choose when"?



## JoshP12 (7 Dec 2020)

Hi all,

*Had a thought: *

How does the plant determine "_when"_ the plant takes up nutrients? Will it take up nitrogen in the light or the dark -- or does it need to be "while synthesis of whatever needs nitrogen" is happening? ... I guess this also applies to CO2 acquisition as well. 

*An example: * If you have ammonia in your water column at lights off (for whatever reason) and you "test" (let's say you can do accurately) in the AM (and it reads a lower number), did the plants take up some of it to use the next day or did the bacteria convert it all?

I do suspect that there is no definitive answer - but was just wondering, so thought I would share.

Cheers,
Josh


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## Zeus. (8 Dec 2020)

I assume it takes up nutrients when it needs them and they are available, if it is full it will take up nothing (or net uptake will equal net loss). There may be primary uptake route which require less energy and if the plant is having trouble getting nutrients it may have secondary routes which may require more energy, if the plant is still hungry it may also remobilise certain nutrients for areas of the plant which receive less light/CO2. I would imagine is a very complex and we have still to find all the answers. 

Ammonium will also be tricky as if their is nitrites or nitrates in the water column the plant may have a preference for one or the other, I am sure @dw1305 will enlighten us


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## Geoffrey Rea (8 Dec 2020)

JoshP12 said:


> I do suspect that there is no definitive answer - but was just wondering



Do you have access to online peer reviewed papers Josh?

A Canadian study from 1997 might help serve as a spine for further literature searches on your questions:


*Models of aquatic plant productivity: a review of the factors that influence growth*​
Carr, Geneviève M ; Duthie, Hamish C ; Taylor, William D
Aquatic botany, 1997, Vol.59 (3), p.195-215


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## dw1305 (8 Dec 2020)

Hi all,


Zeus. said:


> Ammonium will also be tricky as if their is nitrites or nitrates in the water column the plant may have a preference for one or the other, I am sure @dw1305 will enlighten us


The simple answer is I don't know.  I don't have a more recent reference than this one, all the more recent ones I can find are looking at the encoding genes and their activity. I can get a pdf of this if any-one wants it?

This is from <"Gilroy, S. & Jones, D. (2000) "Through form to function: root hair development and nutrient uptake", Trends in Plant Science, *5*:2, pp. 56 - 60>.
Abstract


> ..........In addition, after years of speculation, nutrient transport by root hairs has been demonstrated clearly at the physiological and molecular level, with evidence for root hairs being intense sites of H+-ATPase activity and involved in the uptake of Ca2+, K+, NH4+, NO3−, Mn2+, Zn2+, Cl− and H2PO4−..........


Mechanism


> .......... Because of the lack of suitable molecular and physiological techniques, the mechanisms involved in nutrient capture by root hairs have become clear only recently. Although evidence for the uptake of most major- and micronutrients by root hairs now exists (NH4+ NO3−, K+, Ca2+, H2PO4−, Cl−, Zn2+, Mn2+), the signalling pathways involved in regulating these transport mechanisms remain elusive. Furthermore, it is known that within plant species there is considerable genetic variability in root hair responses to nutrient stress............


For nitrogen (N) uptake it says:


> .........With respect to NH4+ and NO3−, there is now clear electrophysiological and molecular evidence that root hairs can transport N-compounds. Cloning of NH4+ and two putative low-affinity NO3− transporters from tomato38 has revealed that the expression of two of these genes is root-hair-specific (LeNRT1-2 and LeAMT1) and regulated by an external N supply. In the case of the NH4+ transporter LeAMT1, it is constitutively expressed and possibly down-regulated by the presence of NO3−. Indirect evidence using pH-sensitive fluorescent dyes has suggested that NH4+ uptake occurs immediately after the addition of NH4+ to N-starved roots, in agreement with the molecular studies39. By contrast, the NO3− transporters encoded by LeNRT1-1 and LeNRT1-2 are both up regulated in the presence of available....



cheers Darrel


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## dw1305 (8 Dec 2020)

Hi all,


JoshP12 said:


> I guess this also applies to CO2 acquisition as well.


I can do CO2 uptake, it is light dependent and the plant only becomes a net CO2 user / oxygen exporter when <"LCP is past">. What is happening to the CO2 from respiration during the dark period looks to be variable depending on the <"photosynthetic pathways of the plant">, but I would guess for most <"C3 & C4 plants"> it is going to accumulate in the <"internal air spaces of the plant">.

cheers Darrel


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## JoshP12 (9 Dec 2020)

Geoffrey Rea said:


> Do you have access to online peer reviewed papers Josh?
> 
> A Canadian study from 1997 might help serve as a spine for further literature searches on your questions:
> 
> ...



Going to see if I can get a hold of it - thanks.



dw1305 said:


> Hi all,
> 
> The simple answer is I don't know.  I don't have a more recent reference than this one, all the more recent ones I can find are looking at the encoding genes and their activity. I can get a pdf of this if any-one wants it?
> 
> ...



Please, Darrel, I'd love to have access.

That said, I wonder if we could bypass the ammonia leech from aquasoils (and soils in general) if we were able to add complete root systems in the snap of a finger (impossible, I know). That said, maybe it is root development that makes that ammonia leech stop ... a combination of plants and bacteria (hmm ... obviously ... lol) and the equilibrium.  Roots ... more and more I think ADA is onto something .



Zeus. said:


> I assume it takes up nutrients when it needs them and they are available, if it is full it will take up nothing (or net uptake will equal net loss). There may be primary uptake route which require less energy and if the plant is having trouble getting nutrients it may have secondary routes which may require more energy, if the plant is still hungry it may also remobilise certain nutrients for areas of the plant which receive less light/CO2. I would imagine is a very complex and we have still to find all the answers.
> 
> Ammonium will also be tricky as if their is nitrites or nitrates in the water column the plant may have a preference for one or the other, I am sure @dw1305 will enlighten us


Ya - for sure - I recall reading that a strategy to get "rid of" algae was to do a blackout but there was a huge emphasis on dosing the tank during the blackout ... and I thought that was interesting.

Darrel, @dw1305, advised the CO2 part ... but maybe the rest of the nutrients can be taken up as needed (without being triggered from light ... and that would support the dosing vs blackout strategy).

For sure - and here it comes - I think phosphate can  ... but I have no proof!

I think overall cell function is happening readily so we probably just need it all, all the time.

Bottom line .. dose it and move on.

Thanks for helping out everyone!

Josh


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## dw1305 (31 Dec 2020)

Hi all, 
I don't know the answer to this one, but I think there are two separate processes occurring:

Passive uptake of ions, which is driven by diffusion, and 
Active uptake which is dependent upon the transpiration.
Passive intake will definitely occur at all times, dependent upon the relative concentration of ions in the plant and water.

In active transport terrestrial (C3 & C4) plants  only have their stomata open for transpiration during photosynthesis, but I don't know how that applies to obligate aquatic plants without any stomata, my guess is that <"passive uptake is more important to them">.   

cheers Darrel


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## jaypeecee (31 Dec 2020)

Hi @dw1305 

I was specifically looking for a statement in which someone had said that aquarium plants absorb ammonium during the day and also at night. Rather than looking for this any further, may I put the question to you? Can/do aquarium plants absorb ammonium during the day and also at night? It's the 'at night' bit that I'm unsure about.

Thanks in advance.

JPC


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## JoshP12 (1 Jan 2021)

dw1305 said:


> Hi all,
> I don't know the answer to this one, but I think there are two separate processes occurring:
> 
> Passive uptake of ions, which is driven by diffusion, and
> ...



I can't believe I missed this post. Thanks Darrel. 

I wanted to highlight a few things that resonated with me:
1) "adaptations include aerenchyma

gas-filled lacunas 

The thickening and cutinising of the cell walls of external cells, and the hydrophobic surface of the lacunas, prevent oxygen loss to the water environment" 

Basically, the plant is able to saturate itself with oxygen/CO2 and hold it in these gas pockets. Water changing 2 hours after lights on is a great idea - based on this - and I am going to start trying it. Give the plant a chance to get going with photosynthesis, expose its leaves to air with those lights beaming, fill it back up with colder water with even more gas and let it ride. 

2) "However, other species can also use CO2 from sediments

CO2 has been suggested to be produced during photorespiration, or to be transported from the roots"

Acidic soil is good. Push that carbonate equilibrium and suck up that CO2 from the roots. 

3) "In addition, the leaves or fronds (plant tissues that are undifferentiated into stem and leaf) can take in nutrients or water straight from the surrounding environment, and the plants do not completely depend on nutrient uptake via the roots" 

The power of aquatic plants. 

4) "In addition to physiological adaptations at the cellular level, the whole leaf has been suggested to be a machine that supports carbon acquisition by the aquatic plants." 

It actually is all about CO2. 

In conjunction with < this post >, it too precious a commodity to futz around with optimizing it to the environment. Plants are so smart. 

5) "and the ability of these plants to make their leaves polarised. 

The measurements of Em (membrane potential) under different external K+ concentrations and pHs have suggested that this hyperpolarisation is mainly due to an increased activity of H+ -ATPases and K+ channels in the plasma membrane"

Acidic water allows for easier carbon acquisition. 

Potassium is essential for that polarisation - allowing the plant to convert bits of HCO3- into usable CO2. I don't know if all plants can do it as well - but there is no doubt that due to the acid layer, it will be able to absorb that OH- and utilize the CO2. That polarization is possible due to the potassium ion movement. 

The ADA system has low pH and high potassium ... it can't be a coincidence. 

6) "The K+ outward channel was highly selective for K+ and was impermeable to Na+ and other monovalent cations"

Potassium ... vital AND the plant can select it. Now it's a matter of increasing probability of getting it there with less ions in the water column. 

7) @jaypeecee 
"Two transport systems, a high affinity and low affinity system have been suggested to carry out NH4 + transport across the plasma membrane, as well as the transport of other cations" 
From the paper: 








jaypeecee said:


> I was specifically looking for a statement in which someone had said that aquarium plants absorb ammonium during the day and also at night. Rather than looking for this any further, may I put the question to you? Can/do aquarium plants absorb ammonium during the day and also at night? It's the 'at night' bit that I'm unsure about.



Ammonia should be taken up all the time and it should be held in the plant as a source of nitrogen. This would explain ammonia burn - as the plant has no exit for it. So you have to drive the plant hard enough to use ALL that ammonium before it burns the plant. Unfortunately, without limitless CO2 (as photosynthetic rates will increase with higher concentrations (http://www.plantphysiol.org/content/plantphysiol/88/4/1310.full.pdf)), we can't do it -- so the plant burns. 

8) "Only recent studies on Lemna minor have demonstrated that the roots are also involved in N uptake, and that the plants can regulate NO3  uptake via either fronds or roots" 

It picks. Hence the ability for the plant to choose where to get its nitrogen from ... and why we need to deplete the substrate of nitrogen before we see nitrate limiting effects. 


9) Back to that picture: 

It looks like 
N/P are absorbed in their own channel. 

Potassium can go in AND it can go out. NOTICE it doesn't need ATP to export it -- this is likely why people notice no issues with intensely high doses of potassium. 

But Calcium ... it requires ATP to get it out of there  - so what -- more interestingly, Ca and Mg HAVE to use the NSCC (non-selective cation channel) ... that MAY be why people with high Ca report that they need "more micros" or that "it reduces the effects of toxicity"

Interestingly, 




The atomic size of the primary micronutrients that we add to our tanks are similar to Calcium ... and many of their charges are similar ... Now Calcium is bigger so I am not surprised that it messes with getting in there more so than anything else. 

The Mg bit - it also uses that channel ... but it is the smallest -- wonder if it can squeak by - lol. @Zeus - if you ever add 30 ppm of Mg to your tank (with 108 Ca) for a week, please post about it as I want to know what happens .

Think that is all for now! Happy New Year! 

Josh


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## dw1305 (1 Jan 2021)

Hi all, 


jaypeecee said:


> Can/do aquarium plants absorb ammonium during the day and also at night? It's the 'at night' bit that I'm unsure about.


I think passive uptake would occur all the time, so at one level plants will take up ammonium over night via passive uptake. Against that this one suggests that uptake largely occurs during the day <"Diel variation of nutrient retention is associated with metabolism for ammonium but not phosphorus in a lowland stream">, presumably as a combination of active and passive uptake when LCP is exceeded.


> ......... In contrast, NH4+ uptake clearly varied throughout the day. Up to 48% of the observed NH4+ uptake rate could be explained by NH4+ estimated from GPP, and NH4+ demand was positively associated with GPP, indicating a high dependence on photoautotrophic demand. An increase of nitrite (NO2−) concentration during additions (representing up to 70% of the added mass of NH4+) suggests that nitrification contributed to the diel pattern of NH4+ uptake........


I think with all these questions, even if you don't know the answer, you can go back to the <"one legged Irishman and the pile of money"> and make some guesses. 

If something is a scarce resource, <"a low hanging fruit"> there will be strong selective pressures on organisms to "develop" (<"_for mutations to occur_">) pathways for acquisition of that resource.

cheers Darrel


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## jaypeecee (3 Jan 2021)

Hi @dw1305 

Thanks ever so much, Darrel! The abstract from the link you provided is very helpful. For my benefit, what is meant by _active_ and _passive_ uptake?

JPC


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## jaypeecee (3 Jan 2021)

JoshP12 said:


> @jaypeecee
> "Two transport systems, a high affinity and low affinity system have been suggested to carry out NH4 + transport across the plasma membrane, as well as the transport of other cations"



Hi @JoshP12

Thanks for this.

JPC


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## dw1305 (3 Jan 2021)

Hi all,


jaypeecee said:


> For my benefit, what is meant by _active_ and _passive_ uptake?


All transport through a membrane is  along a concentration gradient, in passive transport that uptake depends upon the pre-existing level of ions ion solution on either side of the membrane (the water and the plants internal tissue) and in active uptake the plant alters that internal ionic balance to preferentially take up the ions that it needs <"as described">earlier in the thread  by @JoshP12.

cheers Darrel


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## jaypeecee (3 Jan 2021)

Hi @dw1305 

Thanks very much.

Plants are truly amazing!

JPC


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