Leaf colour in autumn

Ross Koning Koning at ECSUC.CTSTATEU.EDU
Mon Oct 21 07:24:41 EST 1996

At 12:44 PM 10/20/96 -0700, Char A Bezanson wrote:
>Thanks for the summary.  Just one question- I've always been under the
>impression that it was the Mg ion in the center of each chorophyll
>molecule that is the primary object of recycling by trees before
>leaf-drop.  Since Mg++ occupies essentially the same position as Fe++ in
>hemoglobin, its lack would cause the plant equivalent of "iron-poor
>blood"...although I'm sure N is worth retrieving as well.  Do any of the
>plant physiologists out there have any comment on the relative scarcity of
>Mg and N, and of their fate and storage over winter?

One physiologist's perspective...

I cannot say from personal measurements of Mg in plants
and soils, but I was always taught it was the Mg ion
that was the "goal" of the recycling.  I wonder where
the data are that support that idea?  I would guess
that someone HAS done the measurements...perhaps decades
ago.  The nitrogen recycling is likely important too.
I have always considered the hydrocarbon and hydroxycarbon
skeletons as dispensable, explaining the lack of selective
pressure to retrieve the carotenoids and anthocyanins
from leaves.  I have speculated that the rise in the
anthocyanins was a by-product of "mineral mining" in the
leaves.  I like the light-protection theory, though.  I
wish someone would resolve all this in a clearcut "Botanical

I think it would be great to have a modern study of this
whole phenomenon.  The University of Vermont would be a
natural location...


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: 860-465-5213

                Plant Physiology is Phun!

 /\|___/\     //\______COOH   NH-CH2-CH=C-CH2OH  \/OH
|  |  |  |    |  |  ||       //\___     \CH3     /\|/\\/\\COOH
 \/ \/|\/|    \\/ \ /       N  ||  N            |  |
 /\ | |__|=        NH       |  || ||           //\//\
  | COOH                    \\ /\ /            O
  COOH        H2C=CH2         N  NH

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