Stomatal regulation in CAM plants

Peter Werner boe666 at u.washington.edu
Fri Nov 1 01:21:24 EST 1996


How is the opening and closing of stomata regulated in CAM plants? I've
looked through several plant physiology books and they state nothing more
than the obvious - CAM plants open their stomates at night and close them
during the day - but no explanation as to how this is done.

My guess is that their response to light is similar but opposite to that
of other plants. Light activates cytochromes and K+ is pumped *out* of 
the guard cells, water follows, turgor decreases and the stomatal openings
are closed.

I would also guess that CAM guard cells don't respond to CO2 levels,
unlike most plants. In most plants, an increased CO2 proportion in the
substomatal air space is a sign that photosynthesis is slowing down and
light is disappearing. Because CAM plants fix CO2 at night and release 
it during the day, however, they maintain a relatively high level even
while photosynthesizing, hence, it wouldn't seem that CO2 levels would 
be a very useful way of distinguishing day from night in these plants.

Are my speculations about CAM plant guard cell regulation accurate or am
I barking entirely up the wrong tree?

Peter




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