Question

The experiment is about whether the concentration of sodium bicarbonate will have an effect or not on the rate of photosynthesis in spinach by recording the time taken by the leaf disks to float in the sodium bicarbonate solution with different concentrations (0.7% and 1.5%) as treatment groups and the distilled water as the control group.

Is it possible for leaf disks to float in thecontrol group (Distilled water)?

Why do you think the leaf disks floated at different times in your trial run?

What are the potential sources of error? How will you troubleshoot these when running your experiment?

On what basis will you determine the number of replicates to be used?

Answer 1

Yes, in case of control i.e when distilled water is present the leaf disk float on the water. It is because the leaves have air in the space that occur between the cells and it helps the leaves to collect the carbon-dioxide gas from the environment.

The leaf disks floated at different times in the trial run because of the variable concentration of sodium bicarbonate used. The less concentration means less carbon dioxide and hence less sinking of the leaves.

The potential source of error might be understanding the level of carbon dioxide present in the solution. The clear understanding about carbon dioxide level helps in figuring out whether the leaves will float or sink. This can be troubleshooted by controlling adding to the sodium bicarbonate and gradually checking for the carbon-dioxide concentration.

The number of replicates to be used is decided based on level of sinking and floating of the leaf disk.