Nitrogen and its affect on plant color

Phil, if red need more light, why are cactus and desert plants all green and why are tropical rainforest plants deep in the jungle red?

That's counter to the entire notion of red needs more light.
Few emergent plants are red, red plants that grow out of the water become green.

It takes a lot of N to produce Chl, not much to make red which will catch lots of light and make the Chl a more efficient and the plants can have far less N per unit of leaf area.

There are many things a plant can do to get more light or reduce the amount of light.

I do not buy that red plants need more light nor iron. Never have.

Regards,
Tom Barr