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?