Leaf stains solved (?)

Dr. David Starrett dstarret at BIOLOGY.SEMO.EDU
Wed Nov 12 10:35:06 EST 1997


>
>	I spent last summer on a tributary of the Rio Negro in Brazil. The
>acids that
>produced the "leaf stains on concrete" mentioned by David Starrett are
>responsible for
>the "black water" rivers of tropical rain forests. Tropical black water
>rivers and streams
>occur in areas of sandy soils--the sand serving as a tea strainer,
>holding the leaf litter
>back while allowing the leachant to filter into the streams. Some of the
>black water
>streams look very black, like strong tea, while others are more of an
>amber color. 

Thanx for the load of responses.  Tannins seem to get the vote, though
anthocyanins came in a decent second.  Interestingly, my class, which has
14 bright students, most of which have had biochem, came up with the same
first and second choices.  One pointed out to me that when working with
certain types of wood, hands and clothes get stained, and it is hard to
remove.

As to the black rivers, does this mean that the color of tea is due to
tannins?  Do tannins actually have a color, or is the color produced bcause
they react with other molecules?  

Also, I am guessing that this answers the question what are the stains seen
on concrete under a pile of wood, etc.


Thanx again for the prompt responses, I was able to reply to me sudents,
yes, you are correct!


Dave Starrett


***********************************************************
* Dr. David Starrett                                      *
* Biology Department, MS 6200                             *
* Southeast Missouri State University                     *
* Cape Girardeau, MO  63701                               *
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