Procedure
- Measure out 100mL water and place in test tube
- Cut a length of Elodea and add to the test tube
- Put test tube in front of the lamp and leave for significant period of time (5 mins)
- Record qualitative observations
- Repeat steps 1-4 with varying light filters between the lamp and the elodea.
Conclusion
The results gained were purely qualitative as it was difficult to measure any form of quantitative measurement. The only possible indicator available was the production of air bubbles. We observed whether photosynthesis was occurring through the production of air bubbles. We observed the elodea through the various light filters and did not observe any change in the quantity of bubbles produced. As the changing colour filters caused no increase or decrease in air bubble production from the entire visible spectrum we can conclude that light colour has no effect on the rate of photosynthesis.
Evaluation
Our results show that light colour or wavelength has little or no effect on the rate of photosynthesis, however we know that this cannot be true as the elodea contains pigments that absorb certain wavelengths and thus different colours of light, such as chlorophyll absorbing green and xanthophylls absorbing orange. This shows that there is a flaw in our experimental results and thus there must be a flaw in our experimental design. Some wavelengths do not have a concurrent pigment in the plant and thus would not cause any change in the photosynthesis process. However our experiment showed us that the elodea could absorb all the wavelengths of light, something we know not to be true. The filters are a possible source of error, if repeated higher quality filters should be used as well as a better method to shine the light upon the plant.
Photosynthesis – Limiting Factor (Temperature)
Nick Gourlay
Purpose
The purpose of this experiment is to design a procedure to determine how much the rate of photosynthesis varies when the plant is in different conditions. In this experiment the varying condition will be temperature.
Hypothesis
High temperatures will denature enzyme activity; a big increase in temperature will stop photosynthesis. Accordingly, low temperatures will slow down photosynthesis as well, by enabling the plant to gather energy from light and excite its electrons. Therefore, in order for photosynthesis to work, the temperature must not exceed a temperature maximum or minimum.
Experimental Design
The design of this experiment is one which allows us to observe the rate of photosynthesis as it is exposed to different temperatures. We will conduct six experiments at different temperatures (including a control), in order to observe the impact it has on photosynthesis. Three of the samples (containing a plant in a test tube), which will have to be boiled in order to raise their temperature, and two of test tubes that will be cooled, in order to record observations at lower temperatures.
Materials
- Elodea (water plant)
- Graduated cylinders
- Test tubes
- Water
- Thermometer
- Lamp
- Boiling Water
- Ice Water
Procedure
- Measure out 100mL water and place in a test tube
- Cut a length of Elodea and add to the test tube
- At room temperature, put test tube in front of the lamp and leave for significant period of time (5 mins)
- Record qualitative observations
- Repeat steps 1-4 with varying temperatures, place one test tube in the boiling water and place one test tube in the ice water.
Conclusion
The results gained were purely qualitative as it was difficult to measure any form of quantitative measurement. The only possible indicator available was the production of air bubbles. We observed whether photosynthesis was occurring through the production of air bubbles. We observed the elodea under various temperatures and did not observe any change in the quantity of bubbles produced. As the changing temperature caused no increase or decrease in air bubble production we can conclude that light colour has no effect on the rate of photosynthesis.
Evaluation
Our results show that temperature has little or no effect on the rate of photosynthesis, however we know that this cannot be true as we understand that temperature would have an effect upon the rate of photosynthesis. Enzyme activity is required for the process of photosynthesis to occur. We know that enzyme activity is directly related to temperature of the surroundings. The effectiveness of enzyme activity increases with an increase of temperature. We also understand that once a certain temperature is reached the enzyme will denature and cause a slowing of the process of photosynthesis. No bubbles would be expected from the boiling water or the ice water as the enzymes will have become denatured and the process will have stopped. However the lack of air bubbles at the room temperature elodea caused surprise. This showed that there was clearly a flaw in experimental design and results. It is hard to predict what the exact cause for the problem was however it could be due to the method of lighting, or damage to the plant or another substance being present in the water. If repeating the experiment these are areas that should certainly be improved upon.
