RESEARCH QUESTION
How does controlled light intensity and sodium affect the rate of increase in the excess of oxygen created by the elodea plant undergoing photosynthesis?
Four parts of elodea will be used to see how the light intensity have the influence on the process of photosynthesis. The change of photosynthesis will be measured by the amount of oxygen bubbles.
HYPOTHESIS
If the light intensity decreases, then the rate of photosynthesis should also decrease.
Plants receiving the most intense light would produce oxygen faster or in a higher quantity compared to the plants receiving plain room light and no light at all. But, at high light intensities the rate of photosynthesis reaches a plateau.
Independent variables: intensity of light, baking soda
Dependent variable: amount of elodea, temperature
Controlled variable: amount of oxygen
MATERIALS
- 4 cut pieces of aquatic plant (Elodea)
- 4 test tubes
- distilled water (boiled and brought to room temperature)
- Sodium bicarbonate water (boiled distilled water w/.5g of baking soda
- Watch
- Test tube rack
- 4 stirring rods
- Plastic bottle with cap (to aerate distilled water)
- 160 W light bulb
Candidate’s number 002094- 023 Aleksandra Katarzyna Rosiczka
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- Pipette
- marker
- lamp (light source)
- knife/Scissors
- ruler
- 2 pieces of aluminum foil (to cover the sides of test tubes)
PROCEDURES
- Obtain 4 sprigs of elodea in 12 cm long pieces.
- Place one plant against one glass stirring rod. Attach each end to the stirring rod by placing a rubber band on each end. Keep elodea towards one end of the rod. Place
a stirring rod with the elodea in each test tube.
- Place enough distilled water in each test tube to just barely cover elodea.
- In two of the test tubes, place 1 ml of sodium bicarbonate water and mark as test tubes 1 and 2.
- In the other two test tubes, place 1 ml of aerated water. Mark these as test tubes
3 and 4..
- Place test tubes 1 and 2 in the test rack.
- Place aluminum foil the sides of the test tubes 2 and 4.
- Place test tube rack with test tubes 1 and 2 in light source.
- Have two team members count the number of bubbles produced in each test tube for 5 minutes.
- At the same time, two team members will be counting the bubbles produced in test tube 3 and 4 for 5 minutes. Make sure that the test tubes are not exposed to much light.
- After 5 minutes, the team reassembles to document the amount of bubbles in each test tube. All members of the group should have the same information in their notes.
Candidate’s number 002094- 023 Aleksandra Katarzyna Rosiczka ________________________________________________________________
DATA COLLECTION & PROCESSING
Figure 1. Amount of oxygen production
1-Elodea, sodium bicarbonate water, light energy
2-Elodea, aerated water, lack of light energy
3-Elodea, sodium bicarbonate water, light energy
4-Elodea, aerated water, lack of light energy
Figure 2. Measuring of the oxygen production during the process of photosynthesis
Candidate’s number 002094- 023 Aleksandra Katarzyna Rosiczka ________________________________________________________________
Range of the oxygen production in elodea
1st tube
Max. value 44
Min. value 3
2nd tube
Max. value 0
Min. value 0
Rate of the photosynthesis= number of oxygen bubbles/ time
Rate of photosynthesis after 10 min.
1st tube: 0.3 ; 0.2; 0.3; 0.3
2nd tube: 0
3rd tube: 0.4; 0.3; 0.3; 0.4
4th tube: 0
Rate of photosynthesis after 20 min.
1st tube: 17/20; 15/20; 16/20; 15/20
2nd tube: 0
3rd tube: 1, 2.1; 2.1; 2.1
4th tube: 0
Rate of photosynthesis after 30 min.
1st tube: 44/30; 4/3; 4/3; 43/30
2nd tube: 0
3rd tube: 56/30; 54/30; 43/30; 53/30
4th tube: 0
Candidate’s number 002094- 023 Aleksandra Katarzyna Rosiczka ________________________________________________________________
Figure 4. Rate of photosynthesis in elodea
Figure 5. Rate of the photosynthesis in elodea
Figure 6. Rate of the photosynthesis in elodea
Candidate’s number 002094- 023 Aleksandra Katarzyna Rosiczka ________________________________________________________________
RESULTS
In 1st tube the amount of oxygen bubbles was increasing from average 3 oxygen bubbles after first 10 minutes to average 40 oxygen bubbles after 30 minutes whereas in 3rd tube was increasing from average 3.5 oxygen bubbles after first 10 minutes to average 51 oxygen bubbles after 30 minutes.
From this experiment follows that aerated water also accelerates the process
of photosynthesis which means bigger amount of oxygen bubbles.
It can be said that the time of the process of photosynthesis has also big influence on the number of oxygen bubbles- the longer time of the process the bigger amount of oxygen bubbles.
There is no doubt about it that the process of photosynthesis cannot occur without light source. It is proved by 2nd and 4th tube- there was lack of oxygen bubbles all the time –after 10, 20 and 30 minutes.
It is important to mention that the rate of photosynthesis was increasing as well as oxygen production. At the beginning the rate of photosynthesis in 1st and also in 3rd tube was average 0.3. However at the end (after 30 minutes) it was 4/3 in 1st tube and 54/3 in 2nd tube.
CONCLUSION AND EVALUATION
The hypothesis is supported by this experiment. It was proved that the light intensity affects the rate of photosynthesis. If is more light is better. However, too much light cause slows down the rate ( it shows the 3rd trial in 3rd tube). Also lack of light source unable the process to occur as it is in 2nd and 4th tube.
If a lot of oxygen is being given off, photosynthesis is occurring rapidly. If little oxygen
is being given off, photosynthesis is occurring slowly. The amount of trapped light energy and the amount of carbon dioxide available affects the rate of photosynthesis.
Under the given conditions, the elodea being tested were able to undergo photosynthesis. This is apparent by the product created by the elodea. Oxygen released by them showed that photosynthetic reactions had taken place (1st and 3rd tube). Furthermore the amount
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of oxygen generated indicated the rate of which photosynthesis reactions were occurring.
In elodea where the light source was of closer proximity more oxygen products were found to be produced. the light was to the elodea, the greater light intensity it provided.
If there is lack of light source the process of photosynthesis does not occur so the rate
of photosynthesis is equal to 0. This demonstrates that greater light intensity enabled more accelerated photosynthesis as more products were able to form faster.
As aerated water as sodium bicarbonate water contain big amount of CO2. If had not been added, the process of photosynthesis would not have occurred because the distilled water does not have CO2 which is needed for this process. This experiment was based on the light from 160W bulb.
Although the experiment resulted successfully there are several problems that appeared along the work that could certainly be improved so that the results become more accurate. Some errors and solutions to them are presented on the table on next page.
Candidate’s number 002094- 023 Aleksandra Katarzyna Rosiczka ________________________________________________________________
Figure 7. Errors and solutions to them
But besides of the observations made and the errors made, the work was finished and obtained data was relevant and reasonable to determine the affects of light intensity on the rate
of photosynthesis in plants- research based on process of photosynthesis in elodea.
Candidate’s number 002094- 023 Aleksandra Katarzyna Rosiczka
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BIBLIOGRAPHY
A.Allott IB STUDY GUIDES Biology for the IB DIPLOMA Standard and Higher Level, Oxford University Press 2007
A.Allott IB STUDY GUIDES Biology for the IB DIPLOMA Standard and Higher Level, Oxford University Press 2007, page 21
A.Allott IB STUDY GUIDES Biology for the IB DIPLOMA Standard and Higher Level, Oxford University Press 2007, page 21
