Subject: Re: Black plants

From: [email-masked] (Marco_Bleeker)
Date: Sat, 29 Apr 1995 17:54:48

>An interesting thought occured to me about black plants:

>Objects appear black when all the light incident upon them is absorbed
>so an entirely black plant should, in principle, be the most efficient
>for photosynthesis and would _prevent_ light reaching plants in lower
>strata of a canopy that are competing with it!!

  First: we were talking about flowers here, not about leaves and 
photosynthesis.

  Second: a leaf looks green, because the chlorophyl filtered out a lot 
of the red.  Red is the most active wave-length for photosynthesis (to a 
lesser extent also blue).  So, an efficient leaf, that filters out all the 
light it could use, might still look green: deflecting the wavelenghts it does 
not need.

  On the other hand, there are pigments that are able to 'activate' 
wavelenghts of light for photosynthesis. Without these pigments, certain 
wavelenghts would not be used. We find these pigments mostly in seaweeds 
(brown and red algae), perhaps an adaptation to a changed light spectrum at 
greater depths.  So in this sence you have a point: a very efficient leaf 
should be black...  (You stated the opposit - a black leaf is not necessarily 
very efficient).

  Bye, Marco