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Re: Seeing Red

> Red pigment or Anthocyanin is produced as a response
> to UV-B, by a complex enzymatic process. Simply put,
> the sun, or other light that produces UV-B, causes
> this process and not the prescence of a metal. There
> is no iron, or any other metal in anthocyanin.
> (Source: Mark Fisher)

So why does a red onion, with it's tasty red leaves below the surface have
anthocyanins yet the leaves one sees above ground are green?
Seems it should be the other way around if that was true as a

I suppose with some _specific_ plants, this would be true.
Now about the practical application of UV-B in our tank?
Why are the plants red in my tank if I don't add any UV-B?

I get quite red coloration without using UV-B light.

Must be something else. At least in our case specifically and that's the
real question, not some red plant of in a lake or the farm.

The production of anthocyanin may have many other functions and reasons to
Not all red coloration etc is anthocyanin based. Some is caroteniod based,
some is in chromoplast.
Adding iron, while not part of Anthocyanin, will increase Photosynthesis(PS1
and 2) and other enzymes in a number of cycles. These cycles allow for the
production of energy and sugars, of which anthocyanin is part of so
anthocyanin is: Any of a group of glycoside pigments formed by the addition
of sugars and other residues to a precursor(often pelargonidin, delphinidin
or cyanidin). 
Yea, yea, I know that part just means everything and you folks say

"Ahhh!!Now I completely understand!":-)

But in order to get complex stuff in plant biochemistry, you got start with
the basic building blocks, the nutrients. Not just one or two but all of
them work along the way to making all sorts of chemicals.
Plants cannot run away or move like an animal so they have to make do and
make chemicals to fend themselves or else die.

(Anthocyanins) are sap soluble. This is why the plant can change color in a
matter of a day or so in many cases(try the NO3 experiment from 2ppm to
0ppom and raise up to 10-15ppm and then drop it back again etc).

Now you can get nice red plants in low color temps and high color temp and a
mix of color temps. Generally, mostly red and some blue spike yeild the
nicest color IME and what most agricultural ref's mention.

But claims that a certain color of light prevents algae but helps plants,
well, I can tell folks that algae can grow in far more places than plants
can(800ft deep in water, above the tree line, salt tolerant to 10x seawater,
80-90C temps, inside rocks, etc), so ..........algae will grow in any color
temp that will grow a plant.
Going down that road about lighting temps is nothing but marketing crap IMO.
2000K to 20K, algae will be there in one type/species or form or another.
That you can count and rely on.

But I try to hit a nice middle range for lighting, mainly/mostly in the
5000K range with some/one bulb in the 6700-8800K range.

Plants can and do use green light BTW. Chl a and Chl b don't absorb some
light colors but the plants and algae simply use accessory
pigments(Caroteniods and other pigments) to catch the different light
colors/wavelengths. But it take a little time and energy to adjust to the
light if things change. That's not a big issue if things are growing and
there's plenty of nutrients/CO2 etc.
 Tasty red onions sauteed in sesame oil, they'll change color a tad

Tom Barr