koning at ECSUC.CTSTATEU.EDU
Tue Nov 11 15:54:31 EST 1997
At 12:42 PM -0500 11/11/97, Dr. David Starrett wrote:
> 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.
I think you are right about the tannins.
The chlorophyll is usually degraded to
recover the nitrogen and magnesium ion into
the phloem stream before abscission. Tannins
are cheap molecules (CHO) and so are not recovered
during leaf senescence. Anthocyanins and
carotenoids also are also simple molecules and
so have no elements necessitating recovery.
At least that is my understanding of what you
Ross Koning | koning at ecsu.ctstateu.edu
Biology Department | http://koning.ecsu.ctstateu.edu/
Eastern CT State University | phone: 860-465-5327
Willimantic, CT 06226 USA | fax: 860-465-4479
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