Why would a red plant need more light than a green one?

Red plants are found in deeper waters and also in deep jungles, most
red plants are found in darker regions and are considered shade
plants.

Red Ludwigia is found very deep in some springs, the stuff growing by
the surface might be green. I saw this today as a matter of fact.
If the plant is in the same water, why would one be red at 18 ft and
green at the surface?

Red Wendtii was growing in a very shaded portion of the spring, Red
ludwigia was growing in a very deep section of a river. The green
plants were closer to high light than the red plants.

I can grow red plants just fine at less light, so can most people.

Red plants do not need more light than green plants, nor more iron.
Why are many Crypts red? They do very well in shaded conditions.

Plants often turn red when someone puts more light on them due to
increases in growth rates and lack of Chlorophyll near the active new
growth. The increased growth often lowers the available NO3 and
reduces the Chlorophyll, which is rich in N wewreas anthocyanin, the
red color pigment has no N.
The effect of increased light or slight N limitation will cause the
tips to turn red first.

If you watch a red plant break the surface and grow above the water,
it does in fact, turn green in the higher less filtered light.

I think this myth is very difficult to support and I've not found it
to be true in practical terms in aquariums. Some of the reddest plnts
have come from lower light, 2w/gal of NO FL's in 24" deep tanks. You
certainly cannot claim high light is the cause for red color as
generalization. I wouldn't.

Good nutrients, low N etc will promote red color, not high light and
iron anymore than they do for green plants. Low N is a two edged sword
with higher light also. It's easier to maintain a low stable N level
that does not cause a deficiency, vs a higher light, faster uptake
tank.


Regards,
Tom Barr