Stomatal regulation in CAM plants

Pedro J. Aphalo aphalo at
Fri Nov 8 01:31:05 EST 1996

Peter Werner wrote:
> 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

I think your speculations are not very accurate, read section 6.4.1,
pages 147-148 in:

 Willmer,C; Fricker,M (1996): Stomata. 2nd ed. (Series Eds: Black,M;
 Charlwood,B. Topics in Plant Functional Biology, 2.) Chapman and Hall,
 London. 375 pages.

You may also want to look at these papers:

 Santamaria,JM; Herrera,JL; Robert,ML (1995): Stomatal physiology of a
 micropropagated cam plant - agave tequilana (weber). Plant Growth
 Regulation 16(3, May), 211-214.

 Mawson,BT; Zaugg,MW (1994): Modulation of light-dependent stomatal
 opening in isolated epidermis following induction of crassulacean acid
 metabolism in mesembryanthemum crystallinum L. J. Plant Phys. 144(6,
 Nov), 740-746.

I hope this helps,


 Pedro J. Aphalo
 University of Joensuu, Faculty of Forestry
 e-mail: aphalo at                    ,,,^..^,,,

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