CO2 in leaves, correction

Tom Buckley buckley at BIOSERVER.VSB.USU.EDU
Sat Feb 27 17:50:34 EST 1999

My previous post said the net assimilation rate is "respiration minus
photosynthesis" (which is backwards!... whoops) but I didn't point out
that 'respiration' here includes photorespiration.  C4 plants do little
photorespiration and also less maintenance respiration (because they
have much less Rubisco), so their compensation points can indeed
approach zero as Janice pointed out.

Also, the numbers (30-50 ppm) I gave for C3 plants' comp. pts are not
true compensation points, but rather the 'comp. pt. in the absence of
mitochondrial respiration' (an abstraction used in some photosynthesis
models).  A better range for true C3 comp. pts. at 21% O2 would be
50-100 ppm.

Thomas N. Buckley
Biology Department
Utah State University
Logan, UT 84322-5305
voice: 435-797-3567
fax: 435-797-1575
email: buckley at
"Science is the belief in the
   ignorance of experts."
 - Richard P. Feynman
"(Especially when they're
   quoting numbers.)" - tb

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