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RE: Red plants/green plants

>I have a large Ammania which has very pink leaves underwater however all
>of the emersed leaves are very green. Paul K mentioned (on the Crypt
>list) that emersed Crypts are often green whereas the submersed leaves
>can show beautiful red, brown and purple pigmentation. Why is this?
>Steve Pushak                              Vancouver, BC, CANADA 

    Due to less light underwater and the filtering effects of water( when
cloudy, like in many streams)? Marine algae is very similar. Most greens are
near or at the surface while the Red algae has been found in some very clear
parts of the Caribbean Sea to 269 meters or about 880 ft! Not much light
down there! 
    I'm not certain about the Crypts and the Ammania coloration but it does
seem likely that the pigments(such as reds) for wave length absorption are
produced for less light and more light. Crypts don't follow this pattern nor
do Ammania necessarlly either. By adding more light and more light we should
get a green plant submersed but this does not happen.....................at
least in our tanks under submersion.
    Perhaps it is an "automatic" response to submersion that is independent
of light levels?
Typically in nature there would be a dramatic loss of light from submersion
of amphibious plants when water levels rose. The water would be very cloudy.
Little light would get to the plants. The red color pigments are produced to
help it through the wet season........... till the water level went down and
so on.......? Seems like an idea anyway.
Crypts are often grown above water by commercial growers and when get them
home they turn red after awhile even if the lighting is exactly the same. It
can make you downright angry! 
Tom Barr