What Factors Influence Photosynthesis
What Factors Influence Photosynthesis?
Problem: How do different wavelengths of light a plant receives affect its rate of photosynthesis?
Background: Oxygen is one of the products of photosynthesis. Because oxygen is only slightly soluble in water, aquatic plants such as Elodea give off visible bubbles of oxygen as they carry out photosynthesis. By measuring the rate at which bubbles form, you can measure the rate of photosynthesis.
Hypothesis: Write a hypothesis concerning the relationship between light intensity and the rate of photosynthesis.
Objectives: You will:
➢ Observe photosynthesis in an aquatic organism
➢ Measure the rate of photosynthesis
➢ Observe how various wavelengths of light influence the rate photosynthesis
➢ Use the internet to collect and compare data fro other students
Materials:
1000 mL
Three Elodea plants
String
Washers
Colored cellophane, colored light bulbs
Lamp with reflector
150-watt bulb
0.25% sodium hydrogen carbonate solution
watch or timer
[pic]
PROCEDURE:
1. Construct a basic setup like the one shown on the opposite.
2. Create a data table to record your measurements. Be sure to include a column for each color of light your will investigate and a column for the control experiment.
3. Place the Elodea plants in the beaker, then completely cover the plants with water. Add some of the baking soda solution. The solution provides CO2 for the aquarium plants. Be sure to use the same amount of water and solution for each trial.
4. Conduct a control experiment by directing the lamp (without colored cellophane) on the plant and notice when you see the bubbles.
5. Observe and record the number of oxygen bubbles that Elodea generates in five minutes. The bubbles will emerge from the stem end.
6. Repeat steps 4 and 5 with a piece of colored cellophane. Record your observations.
7. Repeat steps 4 and 5 with a different color of cellophane and record your observations.
8. Go to the Glencoe Science Web Site at the following address and post your data. sec/science.
9. Answer the analysis questions. Plot a graph from data collected from other students. (See analysis #3)
10. Write a conclusion for this experiment.
DATA TABLE:
| |Control |Color 1 |Color 2 |
|Bubbles observed in five minutes | | | |
ANALYSIS:
1. From where did the bubbles of oxygen emerge? Why?
2. Explain how counting bubbles measures the rate of photosynthesis?
3. Make a graph of your data and data posted by other students with the rate of photosynthesis per minute plotted against wavelength of light you tested for both control and experimental setups.
CONCLUSION:
Write a conclusion which should include restating the objectives and hypothesis, summarizing and interpreting results, explaining the concept, and stating whether your data supports or refutes your hypothesis. End with a question.
Photosynthesis Lab
Background Information:
Green plants use sunlight to make glucose. To do so, the plant must use carbon dioxide and water in a process called photosynthesis. The glucose made by plants is used by plants and animals as a source of energy. To release the energy contained in the bonds of glucose, the glucose must be converted to ATP. The process by which ATP is made from glucose is called cellular respiration. Respiration also produces waste products including carbon dioxide and water, which are the same substances that served as raw materials for photosynthesis. In water, carbon dioxide dissolves to form a weak acid. As a result, an acid-base indicator such as bromothymol blue can be used to indicate the presence of carbon dioxide. In this laboratory investigation, you will use bromthymol blue to explore the relationship between photosynthesis and respiration.
Problem
What is the relationship between the processes of photosynthesis and respiration?
Materials
2- 125ml flasks, rubber stoppers, 100 ml graduated cylinder, 2 Elodea, light source, drinking straw
Procedure
1. Using a graduated cylinder, measure out 100ml of bromthymol blue solution for each of the two flasks. Caution: Bromthymol blue is a dye and can stain your hands and clothing. 2. Insert one end of a drinking straw into the bromthymol blue in one of the flasks. Gently blow throught the straw. Keep blowing until there is a change in the appearance of the bromthymol blue solution. Repeat this procedure with the other flask. Record your observations in the data table. 3. Place a sprig of Elodea into each flask. Stopper the flasks. 4. Place one flask in the dark for 24 hours. Place the other flask on a sunny windowsill for the same amount of time. 5. After 24 hours, examine each flask. Note any change in the appearance of the bromthymol glue solution. Record your observations in the data table.
Data:
{ Place Data Table Here }
Analysis:
1. What was the color of the bromthymol blue solution before you exhaled into it? After you blew into it? Why did it change color?
2. Why did we use bromthymol blue in this experiment?
3. Why was Elodea place in both flasks?
4. What differences did you observe between the Elodea in the light and the Elodea in the dark? Why did this occur?
5. What is photosynthesis and how do our results demonstrate the requirements necessary for this process to occur?
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