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Re: Anthocyanin

> James wrote:
>>> One very important function of some of these auxiliary pigments is to act
> as
> a form of protection for chlorophyll molecules against the free radicals
> which can be formed within the cells under intense light. Sort of like
> molecular sun shades. In cases where this happens, the red or violet color
> of the auxilliary pigment can visually overpower the green color of the
> chlorophyll and the plant will appear red or purple (Ever see an apple that
> had one side red while the other side was green? The red side was in
> sunshine, the green side was in shade. The apple produced more red pigment
> in the sunlit skin to protect itself from the damaging effects of too much
> light. At least, that's one theory....).<<
> And IMO, not a very good theory when it comes to figuring out why aquatic
> plants turn red.  Most of the bright red plants that we use in the aquarium
> are NOT red when grown emersed in in full sun.  Only the submersed foliage
> is red.  That would make no sense if the purpose is to protect the plant
> from burning in the sun.
> Karen

In the recent literature, the notion that Anthocyanins protect the plant
from excess light does not appear valid. Bioassays have indicated that it
might be an antifungal agent.

I think some folks confuse it with the Xanophyll cycle which is used to
protect against excess light and gives heat, Anthocyanins don't give off
heat, as an early hypotheses suggested.
Tom Barr