Chlorophyll and Green Light

monique at monique at
Fri Nov 1 16:14:20 EST 1996

>A friend asked me a question the other day about chlorophyll.  He was
>wondering why blue and red but not green were absorbed.  After some
>reading and chatting with colleagues I came to the short answer that
>chlorphyll was so efficient with red and blue that there was no
>evolutionary advantage in absorbing green and/or that changes needed
>to absorb green would mean loss of efficiency absorbing blue or red.

As with any pigment, the color you *see* is the light that is reflected, not 
absorbed.  Chlorophyll appears green because it is absorbing red and blue and 
reflecting green.  If it absorbed green, it wouldn't look green (and plants 
would be some other, funny color...)    I seem to remember from plant 
physiology that by the time the atmosphere has gotten through with sunlight, 
red and blue are what there's most of (or maybe what's "best"--it's been a 
long time!)  There must be some advantage or some deep ancestral reason for 
using red and blue, though, because the wavelength "window" used for 
photosynthesis is the same as that used for highest sensitivity color vision 
in the animal kingdom...

Or maybe I'm just nuts...  That's always a possibility

Monique R.

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