Re: [APD] Re: pH's at the leaf's surface, bicarb uptake vs use,

[Chuck Gadd <cgadd at cfxc_com>]

Clint Brearley wrote:

> Are large CO2 fluctuations only detrimental during the day or 
> at night too? Would this mean that turning the CO2 off
> at night would be bad then if CO2 levels fall? Although plants
> don't use CO2 at night, wouldn't the lower night time CO2
> levels "trick" the plants into changing their enzyme production
> and "confuse" them when the light and CO2 kicks-in again in the

While doing research for my AGA presentation a few years ago,
I ran across an article that is somewhat related to this
discussion.

Ground-level atmospheric CO2 concentrations were measured
at several locations, and they found the CO2 level went
thru a daily cycle.

"maximum CO2 concentrations of 440-540 ppm occurring during
a three-hour pre-dawn period that was followed by a
concentration decrease to 350-400 ppm by mid-morning, after
which there was a slow but steady increase in the late
afternoon and early evening that brought the cycle back to
its pre-dawn maximum."

The authors of the study then tested plant growth under
three different conditions
1) constant 370ppm CO2,
2) Constant 370ppm during the day, and 500ppm at night
3) a varying CO2 level from 370 to 500ppm, following
the observed pattern.

Plants from #1 and #2 had identical biomass production
after 29 days, but #3 resulted in 10-21% increase in
biomass over #1 and #2.

http://www.co2science.org/journal/2002/v5n4b1.htm



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