Re: How can I change the amount of carbon dioxide a plant receives?

Ellen:

I discussed your problem with an experienced botany/plant physiology 
technician at the university and here are the ideas we came up with:

CO2 sources:

1. dry ice - perhaps this is available locally from an ice plant or 
bottling plant (donations?).  You could collect the CO2 that sublimes in 
some sort of container or have piped directly into a homemade plant 
chamber.  If it's cold gas (arriving at the plants from the dry ice close 
by) then you could have the inlet at the top of the plant chamber.

2. students - have the students blow into a container or into the plant 
chamber.

3.  your idea of evolving CO2 from a chemical reaction.

I think the bottom line is that somehow you have to keep the plants in a 
closed chamber.  I would put the students to work on this - designing and 
building a chamber from wood frame and greenhouse plastic.  If the chamber 
is sealed (as good a seal as is possible), then the CO2 is more easily 
contained.  Again, it could be piped in from a holding container or 
directly.  To monitor the amount of CO2 present in your chamber, you could 
do some sort of CO2 indicator test (the chemistry teacher should know of a 
simple CO2 test).  Again, the students could be directly involved in the 
monitoring and working out how often they need to fill up the container 
with their own breath.

Well, good luck!