Bio1- Limiting factors with photosynthesis

Question 1

What is the method to test for limiting factors with photosynthesis (6 steps) ?

Answer 1

1. Start by placing a boiling tube 10cm away from a LED light source (these don’t release too much heat)
2. Fill boiling tube with sodium hydrogen carbonate solution. This releases CO2 needed for photosynthesis.
3. Place pondweed into the tube with the cut end at the top.
4. Leave for 5 minutes to acclimatise. Oxygen Bubbles should be seen afterwards.
5. Start a stopwatch and count the number of bubbles per minute. Repeat 2 more times and calculate the mean no. of bubbles produced in one minute.
6. Repeat whole experiment again, but moving the pondweed further from the LED light source each time by 10cm.

Question 2

How can you calculate the volume of oxygen being produced if bubbles are too quick to count in the photosynthesis practical?

Answer 2

Place a funnel above pondweed and catch the bubbles in a measuring cylinder .

Question 3

What is meant by the inverse square law within the photosynthesis practical?

Answer 3

As the distance doubles the number of bubbles reduces by a factor of 4.