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
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.
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.