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Vallisneria - A few questions!

PlatyFINatic

Seedling
Joined
3 Aug 2012
Messages
21
I needed a plant to cover an area at the back of my 55. I went to my LFS and bought 3 bunches of Vallisneria. I had it once before, but soon got rid of it. I then read that it needs high lighting, and my Roma only has a couple of T8s that are about 60w combined. I then started to think - is it gonna grow??

I have a Tetra Complete Substrate underneath play sand and currently do not dose liquid ferts, however I probably will soon!

Have I made a mistake in getting this plant? Is it just gonna die or something in my lower light?

Thanks in advance :D
 
vallis is the ultimate low tech plant it'll grow in anything. I've even got it growin in a 2x1x1 fry tank with no light at all and just gravel for substrate with leafs almost 1m long now :) takes it a few weeks to get rooted/settled then it spreads like a weed
 
Ok thanks! Phew!
 
ceg4048 said:
Rule number 1: There are no such things as plants that need high lighting.

Cheers,

How does that work? :D
 
Grows like a weed.

Just to add, dont use easycarbo product with Vallis (it melts it)
 
PlatyFINatic said:
ceg4048 said:
Rule number 1: There are no such things as plants that need high lighting.

Cheers,

How does that work? :D
people assume, like i did, that plants need high light in which to thrive, not true- they need carbon. This is amplified if high light is used.
 
darren636 said:
PlatyFINatic said:
ceg4048 said:
Rule number 1: There are no such things as plants that need high lighting.

Cheers,

How does that work? :D
people assume, like i did, that plants need high light in which to thrive, not true- they need carbon. This is amplified if high light is used.

Oh right, I see what you mean! I guess some plants that say they do, do? :D
 
As Darren mentions there is a lot to unlearn before we can begin to figure out how to provide the best conditions for plant health.

Everybody knows that plants perform photosynthesis but it seems that very few actually have an idea how it works. Most think it goes something like this;

Light==>Growth

However it is not as direct as that simple schematic. It is more like:

1) Light==>Food Production
2) Food Production==>Food Consumption
3) Food Consumption==>Growth

I've broken it up into 3 separate schematics because they are all very distinct processes, and they really have to be studied independently to make sense of it all.

If you think about it very carefully, you'll see that photosynthesis is really only about schematic 1). Plants make their own food. We have to obtain our food by killing and devouring something else. So plants are referred to as "Autotrophs", which means literally, self-feeding.

Schematic 1) chemically looks like this generally speaking:
1) CO2 + Water + Energy input ==> Sugar + Oxygen

That "Energy input" is the light. The equation is finely tuned so that for a certain amount of quantum energy input, the plant needs to collect a certain amount of CO2 and water in order to produce a commensurate amount of sugar and oxygen. Only a percentage of the cells in the plant are capable of executing this chemistry. These cells are called the Chloroplast cells.

At the same time that the chemistry of Schematic 1) is being performed, the chemistry of Schematic 2) is being performed. Chemically, it look like this, generally speaking:
2) Sugar + Oxygen ==> Water + CO2 + Energy output

Schematic 2) is referred to as aerobic respiration. The chemical "Energy output" is what's used to power Schematic 3), but that's a lot more chemically complicated, so we'll leave that alone for now.

The problem is this; while only a percentage of the plant cells can perform schematic one, and while those special chloroplast cells only perform this function for 8 hours a day, every single cell in the plant needs to respire, otherwise the cell dies. Also, this respiration occurs 24/7. There is no rest for respiration.

Again, If you look closely at the two schematics you'll realize that during the photoperiod, one part of the plant is producing Oxygen while the other areas of the plant are consuming Oxygen. One part is consuming CO2 while the other parts of the plant are expelling CO2. This only makes sense when you think about the schematics and therefore the organization of the plant, i.e the division of labor and the independence of the two processes.

Going a bit deeper we can imaging that there is some "Energy input" level in Schematic 1 (lighting level) which chemically releases the exact amount of Oxygen as the amount of Oxygen needed to be consumed to make Schematic 2) function correctly. When this happens, the "net" Oxygen is zero and the plant is using about as much energy as it is producing. The amount of light at that point is called the Light Compensation Point (LCP).

LCP effectively defines the minimum lighting energy level necessary for the plants survival, below which the plant will starve and above which the plant can produce extra food and will grow.

When people talk about "high light" plants, what they really ought to be talking about is high LCP. Have a look at the simplified graph below. The cyan dotted line is the point at which Oxygen consumption and Oxygen production are equal. As you move to the right (increasing light energy) more and more Oxygen is produced until saturation where adding more light does not improve the Oxygen production. You can see where the line flattens out. So for a give level of CO2 and water you can increase the food production and growth by increasing the light up to a point.
compensation-point-light.jpg


Plants that are very efficient at producing food do not require as much light to do so and so that cyan colored dotted line will move downward so that the LCP for those plants will be a lower brightness. Plants that are not as efficient will require more brightness to break even and the dotted line will move up. They will have a higher LCP.

Ferns and mosses are examples of plants with low LCP. They can thrive in very low light. Exotic stem plants on the other hand have a higher LCP, however, the thing to rmember is that the difference in actual brightness for low LCP compared to high LCP is not that much. Whereas the numbers may differ by 50%-100%, many people assume that they need 500%-1000% more, and that's where the problems begin.

What they forget or never understand is that there is also something called the CO2 Compensation Point. Similarly, for a given level of light energy, this parameter defines the amount of CO2 that is required to have the Oxygen producing cells discharge exactly the same amount of Oxygen as the amount of Oxygen being consumed by the plant. There is a very similar curve:
compensation-carbon-dioxide.jpg


You can see therefore that some plants have that Oxygen net-zero line higher or lower. Many so called high light plants actually have a high CO2 Compensation Point. Of course, it's physically a lot easier to add more light to a tank than it is to competently add more CO2 to the tank, so this complicates the problems even more.

The general rules of thumb to remember is that;
Adding more light requires the addition of MORE CO2.
Adding more CO2 allows the use of LESS light.

Cheers,
 
:clap: typical ceg, just breezes over the science bit. :clap:
 
Lol! I am gonna have to read that when I feel "Scientific"! :p

Thanks for that - I will read it when I can :D
 
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