Effect Of carbon dioxide on rate of photosynthesis

[ccBiologist]

I did an experiment in the lab where we punched out leaf discs, flooded the discs with baking soda via a syringe , then placed in a beaker with water and then recorded the time it took for each disc to rise after being placed in the light box. My results were great however a NaCO3 concentration of 2% had the slowest time? Naturally I expected this to be the fastest.

My explanation for this is that CO2 filled up the most of the air spaces and because it is a dense gas a greater volume of oxygen had to be produced in comparison to the other concentration (0.5%,1.0) before the disc could float. If anyone has an alternative explanation please be free to contribute to this discussion

[JackBean]

Do you think that 50% would work better than 1%?

[ccBiologist]

um well re-thinking my answer before I realized that at the 2% NaCO3 concentration the oxygen produced was used for respiration to produce energy to photosynthesize the rest of the carbonate ions

[JackBean]

And why should it be used in case of 2%, but not in case of 1%?