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Photosynthesis " Limiting Factor

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Photosynthesis - Limiting Factor (Light Wavelength) Nick Gourlay Purpose The purpose of this experiment is to design a procedure to determine how much the rate of photosynthesis varies when different colours from the visible light spectrum are used as the light source. Hypothesis As the light colours change from darker to lighter colours (for example from blue to white), the rate of photosynthesis will vary, in that it will not show any change in the middle of the colour spectrum (since green is reflected by chlorophyll), but will with the rest of the colours (white, red, and blue) because chlorophyll absorbs all colours and reflects green. Materials - Elodea (water plant) - Graduated cylinders - Test tubes - Water - Thermometer - Lamp - Light filters Experimental Design The design of this experiment is one which allows us to observe the rate of photosynthesis as it is exposed to different colours of light. For photosynthesis to occur the presence of light is needed, (white light permits plants to absorb all colours of the spectrum except for green, which is reflected). ...read more.


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. ...read more.


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. ...read more.

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