# Effect Of carbon dioxide on rate of photosynthesis

• Author
Posts
• #16878
ccBiologist
Participant

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

• #112533
JackBean
Participant

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

• #112534
ccBiologist
Participant

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

• #112538
JackBean
Participant

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

• #113889
snowfall
Participant

When the concentration of CO2 is low the rate of photosynthesis is also low. (the plant has to spend time waiting for more CO2 to arrive). Increasing the concentration of CO2 increases the rate of photosynthesis.

Experiment

Place a pond weed Elodea upside in a test tube containing water at 25°C.
Place the tube in a beaker of fresh water.
Place excess sodium bicarbonate (NaHCO3) in the water to give a constant saturated solution of CO2.
Place the lamp (the only light source) at a fixed distance from the plant.
Maintain the room temperature at 20°C.

Count the number of oxygen bubbles given off by the plant in a one -minute period. This is the rate of photosynthesis at that particular concentration of CO2.
The gas should be checked to prove that it is indeed oxygen – relights a glowing splint.
Repeat at different lower CO2 concentrations by using different dilutions of a saturated solution.
Graph the results placing CO2 concentration on the x-axis.