Rate of Photosynthesis

Question 1

What are limiting factors of photosynthesis?

Answer 1

Temperature, light intensity, CO2 concentration, amount of chlorophyll

Question 2

Describe an experiment to investigate the effect of light intensity on the rate of photosynthesis using an aquatic organism such as pondweed

Answer 2

Set up a boiling tube containing 45 cm3 of sodium hydrogencarbonate solution (1%). Allow the tube to stand for a few minutes and shake to disperse any air bubbles that might form.
Cut a piece of the pondweed, Cabomba. The pondweed should be 8 cm long.
Use forcepts to place the pondweed in the boiling tube carefully. Make sure that you don’t damage the pondweed, or cause the liquid to overflow.
Position the boiling tube so that the pondweed is 10 cm away from the light source. Allow the boiling tube to stand for five minutes. Count the number of bubbles emerging from the cut end of the stems in one minute. Repeat the count five times and record your results.
Calculate the average number of bubbles produced per minute. Repeat the experiment at different distances away from the light source.

Question 3

What is the independent variable of the pondweed required practical?

Answer 3

distance from the light source/light intensity.

Question 4

What is the dependent variable of the pondweed experiment?

Answer 4

the number of bubbles produced per minute.