oxygen uptake at night

Jon Monroe monroejd at jmu.edu
Mon Jun 25 16:11:54 EST 2001


Carl Pike wrote:
> 
> please post the responses!

Well here they are so far:

My understanding is that, unlike water vapor and CO2, the diffusion
constant for O2 through the cuticle allows for its free exchange with
the atmosphere.  I think that Park Nobel's physiology text has equations
for this exchange and I could look them up if need be.
"Gerald F. Deitzer" <gd3 at umail.umd.edu>

[A very good reference on my shelf if I had remembered to look! - thanks
for the reminder]


Carbon dioxide and oxygen can both diffuse across the cuticle to some
extent, but the concentration of oxygen in the atmosphere is
sufficiently high (21%) that enough will make it, while that for CO2 is
low (350 ppm) so stomates are necessary. 
"Artus, Nancy N." <nartus at wcupa.edu>


The amount of oxygen in a microliter of air (say 8 nmol) is much greater
than in the same volume of air-saturated water (say 0.25 nmol). Thus
there is a large reservoir in the air space of any leaf tissue.
"Raymond P. Cox" <r.p.cox at dou.dk>


The standard wisdom, which I have not questioned or investigated, is
that O2 consumption is so low that even closed stomates have sufficient
conductance to satisfy the plant's needs. It's an 
interesting question, though. O2 consumption is the standard explanation
for the existence of lenticels, but lots of plants don't have lenticels....
"Bill Williams" <WEWilliams at smcm.edu>


I think I remember reading somewhere in the distant past that dark
respiration saturates at oxygen concentrations around 2%, meaning that a
plant has 10X more oxygen than it needs for all out repiratory activity
at any time of the day or night...
"Diane Robertson" <robertdc at grinnell.edu>


Thanks!

Jon

---------------------------------------------------------
 Jonathan D. Monroe                 Associate Professor 
 Department of Biology, MSC 7801   office: 540-568-6649 
 James Madison University             fax: 540-568-3333 
 Harrisonburg, VA 22807         email: monroejd at jmu.edu 
    http://csm.jmu.edu/biology/monroejd/jmonroe.html 
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