An Investigation into the Effect of Light Intensity on the Rate of Photosynthesis on a Piece of Elodea
1) First I will put some water into a boiling tube and add 5 spatulas
of Sodium Hydrogen Carbonate. I will add 5 spatulas of Sodium Hydrogen
Carbonate as it reacts with water and forms carbon dioxide; also I
have so much so that I have carbon dioxide in excess.
2) Then I will cut off 5cm of elodea and place it into the boiling
3) Thirdly I will place the boiling tube in a test tube holder 5cm in
front of the light source.
4) Then I will count the number of oxygen bubbles that rise to the top
in 5 minutes.
However it can get to a point where even though the
light intensity increases the rate of photosynthesis doesn't because
the chloroplasts are working as hard as they can.
The previous method that I used was insufficient for me to get the
results that I required. My previous method involved me connecting a
delivery tube to the boiling tube and attaching that to another
boiling filled with water. The idea was that the oxygen produced would
go through the delivery tube and collect in the other boiling tube.
However the problem with this was that if there was any air in the
delivery tube the oxygen from the elodea would jus get to that point
and stop there. As well as that the air in the delivery tube would
also go down into the boiling tube filled with water. Therefore I
never used this method as my results would have inaccurate and as well
as that there was no way of actually measuring how much oxygen was
Distance from light source (cm)
Number of bubbles produced in 5 minutes
Average number of bubbles
The trend in my graph shows that as the distance from the light source
increases the average number of bubbles produced increases too. I can
see this as there is a positive correlation on my graph and the
average number of bubbles produced for 5cm was 16.33 and for 20cm it
The process of photosynthesis is used to make food in plants. The
formula for this process is:
[IMAGE]Carbon Dioxide + Water Glucose + Oxygen
[IMAGE] 6CO2 + 6H2O C6H12O6 + 6O2
Photosynthesis takes place in the leaves of the plant.
Carbon dioxide is obtained from the surrounding environment. It
diffuses into the leaf from the stoma pores on the underside. Carbon
dioxide increase the rate of photosynthesis until it reaches a
threshold level, where the rate becomes limited by another factor.
This graph shows the effect of carbon dioxide
on the rate of photosynthesis
Water is delivered from the roots to the leaf via the xylem tube. It
is obtained by the roots under the ground. Water, similarly to carbon
dioxide, increases the rate of photosynthesis and it also reaches a
point where it doesn't increase it anymore, because it is limited by
This graph shows the effect of water
on the rate of photosynthesis
Glucose is a product of photosynthesis. It's is used for respiration
in plants. As well as that glucose is a plants source of food. It's
transported around the plant in the phloem vessel....