My guess would be that tannins are involved. Tannins are phenolic polymers
used to tan leather and which give tea its characteristic color. You could
try staining concrete with tea to see if you can duplicate the effect.
Denture cleanser commercials often try to remove tea stains.
Taiz and Zeiger's Plant Physiology text describes the role of tannins as
feeding deterrents to herbivores.
*********************************************************************
David R. Hershey
Snail mail: 6700 Belcrest Road #112, Hyattsville, MD 20782-1340
Adjunct Professor, Biology/Horticulture Dept.
Prince George's Community College, Largo, MD 20772-2199
Email: dh321 at pgstumail.pg.cc.md.us
*********************************************************************
On 11 Nov 1997, Dr. David Starrett wrote:
> Plant-edders,
> Walking across campus I notice the familair leaf stains on concrete
> sidewalks. Some are very good images and show perfect leaf outline and
> even major venation. I asked my Plant Phys class how they occur.
> Now, I need to make sure I have an answer. This doesn't occur with green
> leaves. I am assuming that water is leaching some pigments, tannins, etc
> out of the leaf. Either chlorophyll isn't soluble, doen't stain, or
> remains within a living leaf. What is it that is staining the concrete?
> It is apparently water-soluble. On a hill, the stain smears to the
> downhill side, with streaks often maintaining leaf width.
> Anyone have some good answers I can relay to my students to maintain my
> front as a knowedgable Plant Physiologist.
>>> ***********************************************************
> * Dr. David Starrett *
> * Biology Department, MS 6200 *
> * Southeast Missouri State University *
> * Cape Girardeau, MO 63701 *
> * Ph: 573-651-2382 *
> * Fax: 573-651-2223 *
> * Email: dstarret at biology.semo.edu *
> * URL: http://biology.semo.edu/web/starrett/starrhpg.html *
> * *
> ***********************************************************
>
