![Photosynthesis Lab<br />Introduction<br />Colornmviolet-blue400-525green-yellow525-625orange-red625-700Table 1: Wavelengths spectrumFigure 1: Action spectrum of photosynthesis (Allot).Photosynthesis is a process used by autotrophs to produce their own organic substances. It is when light energy, usually in the form of sunlight, is converted into chemical energy. Autotrophs such as plants contain pigments in which they are able to absorb light. This pigment is called chlorophyll. Although referred to as white light, sunlight is made of many wavelengths including red, green and blue. Particular wavelengths of light allows for a faster rate of photosynthesis due to the structure of chlorophyll. <br />The equation for photosynthesis is: 6CO2 (carbon dixoide) +6 H2O(water) light C6H12O6 (glucose)+ 6O2 (oxygen)Photosynthesis involves the production of oxygen, the uptake of carbon dioxide and an increase in biomass. These three factors can be used to measure the rate of photosynthesis. Production of oxygen effects photosynthesis because as plants are put into water, bubbles of oxygen are released. Oxygen is released as the plant goes through photosynthesis. Therefore, the more oxygen produced by a plant, the faster the rate of photosynthesis.<br />Factors affecting the rate of photosynthesis may include amount of light, carbon dioxide, concentration and temperature. Color affects the rate of photosynthesis due to the different color of wavelengths. A spectrum is a range of wavelengths of electromagnetic radiation. For light, the wavelengths are measured from 400 nm to 700 nm. The measured nm for each color is demonstrated in Table 1. The efficiency of photosynthesis is not the same in all wavelengths of light. Not all light is absorbed through photosynthesis. Figure 1 shows an action spectrum of photosynthesis which shows the percentage use of the wavelengths of light in photosynthesis. From the graph, it can be seen that colors such as violent, blue and red are more efficient in absorbing light than green.<br />Design <br />Research questionWhat is the effect of different wavelengths on the rate of photosynthesis?<br />VariablesThe independent variable in this experiment was the wavelengths. The dependent variable that is affected was the rate of photosynthesis measured by the amount of time leaf discs need to float. Several controls were kept during the research to ensure the highest accuracy possible in the data. Firstly, the same leaves from the same source were used throughout the experiment. Temperature was kept constant by keeping air conditioning on and conducting the experiment in one location. The same amount of water, 100 ml, was used in each beaker with a 2% concentration of sodium bicarbonate, also known as baking soda. The amount of light was kept constant by using the same light source and measuring the light intensity using LoggerPro. The same amount of food dye was used in each solution of the same color. <br />Materials<br />,[object Object]](https://image.slidesharecdn.com/photosynthesislab-110303224004-phpapp02/85/Photosynthesis-Lab-1-320.jpg)
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Photosynthesis Lab
- 2. Hole puncher
- 5. Flasks
- 6. 2500 ml of distilled water
- 7. Syringe
- 8. Sodium bicarbonate (baking soda)
- 9. Source of light (lamp)
- 10. Pipette
- 11. Light sensor
- 12. Tape
- 13. LoggerPro
- 14. Food coloring (violet, blue, green, orange, red)
- 15. Mass scale
- 17. Fill five beakers with 500 ml of distilled water using a graduated cylinder to measure. Make the distilled water a 2% concentration of sodium bicarbonate. To do this, measure 10 grams of sodium bicarbonate on a mass scale and pour it into a beaker with distilled water. Stir. Repeat for all five beakers.
- 18. Set up LoggerPro and the light sensor, making sure it stays in place. Turn on the lamp. Set up light so that it is stable and hits a flat surface directly in front of the light sensor. Place a beaker with the sodium bicarbonate solution where the light hits in front of the sensor. Mark the place by making a square with tape. Keep the set up of the lamp, light sensor and marked location constant throughout. Using a pipette, slowly add a color of food coloring to the beaker measuring the light intensity of the water on LoggerPro. Stop adding food color once the light intensity has reached 350 nm. Repeat for all five solutions using a different color of food coloring for each beaker.
- 20. Blue and GreenThe two-tailed P value is less than 0.0001.By conventional criteria, this difference is considered to be extremely statistically significant.
- 21. Green and OrangeThe two-tailed P value equals 0.0011.By conventional criteria, this difference is considered to be very statistically significant.
- 23. Uncertainty = calculated on Graphpad.com Conclusion<br />There is no constant correlation between the wavelength of light and the rate of photosynthesis, shown in Figure 3. As the time for the leaf disc to float increases, the rate of photosynthesis decreases. The slower time is a result of a lower percent of light absorbed during photosynthesis shown in Figure 1. Each wavelength (nm) has a specific absorption rate. <br />Red, green, blue, orange, and violet took the most to least time for the leaves to float, respectively. All values are supported by the graph in Figure 1. Different wavelengths affect the rate of photosynthesis. The wavelength of light where the leaves take the most time to float is at 700 nm, red. This supports the action spectrum of photosynthesis shown in Figure 1 where red has the lowest percentage of light absorption resulting in a lower rate of photosynthesis of less than 5%. The green light is not effective in photosynthesis because the green light is reflected. This results in chloroplast and causes the leaves to be green. Purple, the solution which took the least time for the leaves to float has a wavelength of around 425 nm. The average seconds it took for the leaves to float is 453 seconds. Purple has an 80% absorption rate. The data supports the hypothesis as the higher rate causes a faster time for the leaves to rise. This makes purple the wavelength that with the optimum photosynthesis rate.<br />The importance of photosynthesis is the reduction of carbon dioxide output. The photosynthesis absorbs carbon dioxide and releases oxygen, helping to eliminate the process of global warming. <br />Evaluation<br />There are several possible errors during the experiment which may have an affect on the accuracy of the data. Firstly, when measuring the light intensity of the solution, it was difficult to get steady results. Although the target light intensity was set at 350 nm, when measured it was ranged from 330-370 nm. This can be fixed by being more careful with the solution and being more careful when dropping the food coloring. Because there were several groups doing the experiment at the same time, there were several disturbances which may have affected the data. People may have accidently blocked the light source or shifted the beakers slightly when measuring. People also had their own light source which may have interfered with the test. Having a full room also means that people are walking in and out. This results in sunlight coming in from the doors. Also, although the windows were covered with blinds, some light still came through. This can be fixed by doing the experiment in a closed room with no windows and no light source except for the one used to conduct the experiment. <br />Works CitedAllot, Andrew. IB Study Guides: Biologywww.graphpad.com<br />