preliminary ideas for a lab

Carsten Richter h0367naa at rz.hu-berlin.de
Fri Jan 16 04:48:46 EST 1998


> I got to thinking for a lab about having students measure metabolic rates
> of various vegetables (isn't there some standard lab done w/ peas in a
> thermos, or peas in some sort of device that captures CO2?), to see first
> of all if it's true about the metabolism of green beans.
> 
> Anne Heise
> Washtenaw Community College
> Ann Arbor MI

Hello Ann, 
as a first shot, you can put your peas in a pressure stable, gastight
container and add some soda lime (solid mixture of NaOH and Ca(OH)2).
You have to be able to measure the pressure inside the container.
If your peas are respirating, you will find a decrease in pressure
because the peas are using the oxigen and evolving carbondioxide, which
will be absorbed by the soda lime. With the time needed for a certain
decrease in pressure, you can carry out a calculation for the
respiration rate.
This sounds easy, but you have to think of certain things.
For example:
The peas will evaporate water and increase the humidity, this will
increase the pressure.
The temperature has a great influence.
The amount and weight of your peas has influence.
With consumption of oxigen, the respiration rate will decrease.
...

Carsten Richter
Humboldt-University Berlin



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