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John Skillman jbs11 at psu.edu
Mon Nov 10 14:34:49 EST 1997

Here's a question Doug Bielenberg and I have been pondering that might
be interesting for the group to consider:
What is the mechanism by which a plant recognizes that a leaf is below
the CO2 compensation point?  This is often used to explain why shaded
leaves begin to senesce.  Why doesn't the leaf just become a sink for
carbon?  It doesn't just starve does it?  If the CO2 compensation point
or a negative carbon budget is the cue for leaf senescence what is the
mechanism?  It may be pertinent to recall that leaves can have functions
other than just carboon acquisition; e.g. nutrient stores used for
growth elsewhere in the plant, transpirational "sinks" driving nutrient
uptake, modifiers of canopy microclimate, etc. etc.
Any ideas on this topic?
John Skillman

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