Phosphorus & Roots

[juggler]

In Diana Walstad's book "Ecology of the planted aquarium" pg 106, her research showed that plants prefer root uptake of the P.

This made me wonder if it is because of this reason that certain plants sprout roots midway from the stem just to absorb the P? Especially if the water is higher in PO4 levels.

Such plants I have in mind are Hygrophila sp, Cabomba sp, some Ludwigia sp or even the Lobelia cardinalis.

Last week I pumped in extra 1.0ppm of PO4 to up the PO4 to 1.5ppm. And this week, I noticed one of the Bacopa caroliniana and most of the Lobelia are sprouting roots from mid-stem.

I don't remember these two plants having roots on their stems before.
I can be wrong. Anyone has similar observations?

Thanks.

[Allen_1971]

I don't have any scientific evidence to back what I'm about to say, so I could be dead wrong... but I seriously doubt it.

Speaking of phosphates, I was thinking of grabbing some KH2PO4 from you... when is a good time for me to pop buy (pm me pls)? Will bring my daughter and we can see who's kid is bigger in size...

[Addie]

Hi Allen and juggler,
Just wonder what is the recommended range of PO4 in planted tank. I recalled the test kit mentioned between 0.1-0.2ppm but never mentioned what type of tank.

Thanks.

[juggler]

The Sera PO4 test kit recommends keeping it within 1.0ppm.

Try reading these articles:
List of Recommended Levels by Tom Barr -- he recommends 0.2 ~ 0.5ppm
Calculating dosages of fertilizer elements for a planted tank by Chuck Gadd -- he recommends 0.5 ~ 1.0ppm

For me, normally I would try to stick within 1.0ppm to play safe. But so far it has not exceeded 1.0ppm even when NO3 is high in the 40ppm range.

[Allen_1971]

addie,

not sure what you mean by "type of tank"? Also, please take care when dosing phosphates... too much can lead to a massive algae bloom.

[Addie]

Bros, thanks for the replies.

Allen,
I thought there maybe some recommended differences of PO4 for planted tank versus non-planted tank. I've not been using PO4 for my tank as the level is ~0.5ppm last week. My tank is only 1 month old after replanting everything due to BGA attack. To play safe, I will keep PO4 below 1ppm.

[Allen_1971]

Addie,

As long as you have a discernable amount of PO4 in your tank it should be ok... So if you have 0.5ppm, then keep it there. No need to go any higher.

[vinz]

You do not want PO4 in any freshwater tank accept a planted tank. In a non-planted tank, PO4 is not used up and it all goes to algae. That's why you need to change water for bare tanks more often, to dilute the PO4 and NO3.

[bclee]

Having PO4 level >1 ppm do not always lead to algae. Pointing finger at PO4 to be the culprit for algae outbreak is not right. Something else must be wrong if there is algae outbreak.

Basically supplying all that is needed by the plants for healthy growth is the key.

I am constantly having > 5ppm PO4 without algae problem. (Thanks to my itchy fingers pulling out plants after inserting Horti tabs in the substrate.) As shared before, my PO4 went up as high as 20+ppm.

Of course, there is no need and no reason to keep PO4 so high. (My case is an accident.) But having PO4 >1ppm is not end of the world. But in case you have an algae attack, I think one may not need to "die die" force the PO4 level down. Just make sure other parameters like CO2, etc keep up to the level needed by the plants.

Just sharing something I experienced...

BC

[bclee]

By the way, with 5ppm PO4, I am not experiencing my Bacopa caroliniana putting out roots from the stem.

Lobelia cardinalis will always sprout roots from the stems.

BC

[Allen_1971]

If the PO4 levels really are the cause of roots coming forth from the stem, then I would conjecture that the lack of PO4 in the substrate is causing the plants to send out roots along the stem, and not the high level of PO4 in the water... still, I think this is unlikely.

KF,

mebbe you can experiment and plant lots of PO4 containing tabs into the substrate near your plants which are sending out roots...

[toshi]

Juggler,

I routinely dose P04 in my setups - I have grown very large, dense groups of Lobelia & Bacopa. Both produce internodal root growth readily, Lobelia closer to substrate level.

toshi ~ san francisco
http://Toshir0.tripod.com/

[Allen_1971]

btw toshi,

I was just poking around the pharmacy yesterday, and was examining the fleet enema available here... the tip is lubricated with some gel which I suppose is meant for easy insertion up the anus. Do you wipe this off? Can you also share your dosing regime with fleet enema?

Also, does anyone know the chemical composition of sodium phosphate and sodium biphosphate?

[juggler]

Thanks for all response. Looks like not conclusive.

Just one more observation on the floating Limnobium laevigatum (South American Frogbit). Sometimes it sends down 6"~7" long roots past half the water column height. But sometimes the roots are very short like 1" and w/o root hairs. Does that also point to some nutrient excess/deficiency in the water?

[Allen_1971]

Perhaps? I would say that the root length would correspond somewhat to the size of the plant above... so if the norm is for a plant of size X to have root length Y, then a root length of greater than Y might imply some deficiency? Sounds plausible enough. Once again no scientific data to back me up, just some logical thinking and (hopefully) common sense.

[CK Yeo]

I doubt that nutrient deficiency/ abundunce is the sole reason for root length... or whether they are above or below the substrate. i.e. I think other environmental factors come into play as well.
There was a study to see where the plants like to uptake nutrients. I can't remember the details of the experiment, but essentially, they used radioactive materials... the conclusion was that which part of the plant takes in more nutrient depends on which part is bigger. i.e. If it was a stem plant, and 95% of the plant is above the substrate, it makes more sense for the plant to take nutrients from the water. vice versa.

However, the matter is more complicated than that, I suppose. If the water is nutrient poor compared to the substrate, the plant will have to depend on their roots to do the job of nutrient uptake, rite? Roots grow more elaborate below the substrate to harness the abundunce of the resources.
Perhaps in some plants, roots are still more efficient in nutrient uptake as compared with the leaves (evolved that way?). So when you fertilize the water column, some plants take advantage of that and grow roots along the internodes to more effectively grab nutrients... however it doesn't do it unnecessarily (i.e. in nutrient poor environment), since they are not photosynthetic and will take energy to maintain them.

For the case of Lobelia (small form), I think it is just their growth habit.... since even in the emersed form, it grows roots all along the stem, although not as long as it would be in the submersed state. like someone mentioned in another thread, it is natural for Orchids to grow aerial roots.

ck

[Allen_1971]

probably true. However, I don't think we are considering whether nutrient deficiency is the ONLY factor affecting root length, but rather we are considering if given a situation where all other factors are similar, does nutrient deficiency/abundance affect root length?

Also, we were discussing root length in the specific context of KF's frogbit. This is a floating plant, and as such quite obviously relies on its root system for nutrition. Given such a circumstance, it seems quite logical that for a given plant of size X, its root length could indicate some nutrient deficiency or abundance.

[geoffrey]

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On 12/17/2002 9:05:26 PM

Having PO4 level >1 ppm do not always lead to algae. Pointing finger at PO4 to be the culprit for algae outbreak is not right. BC
----------------

It seems, based on BC's experience, that having a high PO4 doesn't necessarily lead to algae if all other nutrients, CO2 and lighting are in balance, does that mean then that if a tank is off balance due to PO4 deficiency, that will also lead to algae?

I am having a serious bout of BBA now and when I measured my NO3, it was zero while PO4 is 0.5ppm, Fe=0.25ppm. I do about 1 bubble of CO2 every 2 sec now. I am always skeptical and afraid to bring up NO3 and PO4 for fear of more algae. Both are labelled as the bad guys very often.

I came up with this stupid camel hypothesis, which I told KF, and starved my plants from having the much needed NO3 for 4 days, hoping the plants with its reserve would outdo the BBA from the limiting NO3. But it did not happen, instead my plants suffered, big time! And I lost my first N. japonica's flower bud before it could flower!

I will be very grateful if all of you could help me change my negative mindset about NO3 and PO4 by reaffirming the simple message, "a tank of healthy plants minimise algae."

Go ahead guys, you can scold me for my stupid mistake now.

[Allen_1971]

"A tank of healthy plants minimise algae" is only half true. But a tank of healthy plants in a tank with unbalanced nutrients and you get a tank of healthy plants and algae... which could soon lead to a tank of healthy algae and not so unhealthy plants.

at the end of the day, NO3 and PO4 are nutrients utilized by plants. The statement that high levels of PO4 will cause algae bloom is a guide, and should be seen as such. At the end of the day what ultimately determines if you get an outbreak in algae is how well your plant uptake of nutrients is balanced with your fertilization regime.

Given that algae is also a plant (with the exception of BGA), it competes with your plants for the same nutrients... except that your plants have some "advantage" when it comes to consuming available nutrients... In a sense, your plants get a main meal of whatever you put in, and the algae gets the scraps... leave too much scraps, and the algae starts to gain the advantage by multiplying faster and outdoing the plants. Thats when you get an algae bloom.

[geoffrey]

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On 12/18/2002 4:39:33 PM

Given that algae is also a plant (with the exception of BGA), it competes with your plants for the same nutrients... except that your plants have some "advantage" when it comes to consuming available nutrients... In a sense, your plants get a main meal of whatever you put in, and the algae gets the scraps... leave too much scraps, and the algae starts to gain the advantage by multiplying faster and outdoing the plants. Thats when you get an algae bloom.
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Allen,

That is where I am confused. Algae are plants too, right. Given a tank of well balanced nutritional level, algae and plants will be siphoning them concurrently and simultaneously, right. Before the nutrients are completely sucked up for scraps to build up (and I don't think, correct me if I am wrong, algae will wait for scraps of NO3 or PO4 arising as a result of imbalance to start uptaking them), we replenished and the whole process goes on. Plants and algae continue to grow. Allen, help me out, I still can see how there is an advantage for plants.