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
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:
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