I am going to investigate the amount of light used in photosynthesis to see if it has a noticeable effect when you increase or decrease the light intensity. Photosynthesis is the way in which light and carbon dioxide are used by a plant to produce energy in the form of starch. The factors that affect the rate of photosynthesis are the amount of light, the amount of carbon dioxide (CO2), and the temperature that can be used by the plant.
I have already carried out the experiment to see the effects on a plant when you change the amount of carbon dioxide. I found that the more carbon dioxide used, the faster the plant photosynthesizes. To see if this rule (more of a limiting factor = the quicker the rate of photosynthesis) works, I will plan an experiment. My experiment will be to see if the light intensity follows this rule.
I will use an aquatic plant as it can be used to observe the effects underwater. These plants still contain chlorophyll, a light-absorbing dye that converts light energy into chemical energy. To see if the amount of light intensity will affect the rate of photosynthesis, I predict that the more light you allow the chlorophyll to absorb, the quicker the rate of photosynthesis will be. I think this because the amount of light is a limiting factor in the reaction of photosynthesis.
So, if you allow more of a limiting factor to be present in the chemical reaction, it will almost certainly speed up the rate of that reaction. If a plant has the right amount of carbon dioxide and temperature but the wrong amount of light, the reaction of photosynthesis will be slow. This is because the reaction needs light to let the plant turn the light on.
To conduct the experiment:
- Place the pond weed inside the upside-down funnel.
- Add 1 spatula of sodium bicarbonate inside the upside-down funnel.
- Set the lamp (that’s connected to the power pack) to the chosen distance, either 10, 20, 30, 40, or 50cm away from the beaker.
- Start the stop clock and time for three minutes.
- Count the number of bubbles that the pond weed gives off.
- Repeat this experiment 6 times using a different distance each time.
- Take results for the same amount of time using the same amount of sodium bicarbonate.
Distance of Lamp | Bubbles Realized | Average from the Plant in 3 Minutes
A graph to show the effects of light on the rate of photosynthesis.