Photosintersis Experiment
Measuring the Effect of Light
Intensity on Photosynthesis
Introduction
Photosynthesis captures energy from sunlight. Plants, algae, and some bacteria use the energy captured during photosynthesis for their metabolic reactions. During photosynthesis in plants, chlorophyll and enzymes in leaves convert certain wavelengths of light into chemical energy. A simple equation can be used to represent photosynthesis.
Enzymes and Chlorophyll light energy CO2 H2O carbohydrate O2
In this investigation you will examine the relationship between the amount of light energy available and the rate of use of carbon dioxide by a plant in the process of photosynthesis.
Problem
What is the relationship between light intensity and the rate of photosynthesis? Pre-Lab Discussion
Read the entire investigation. Then, work with a partner to answer the following questions.
1. What are the variables in this experiment? Identify the manipulated and responding variables and two controlled variables.
The manipulated variable is light intensity. The responding variable is pH. Controlled variables include the initial pH, the size of the plant sprigs, and time.
2. How will you provide carbon dioxide to the evergreen sprigs?
Carbon dioxide is provided by blowing into the BTB solution.
3. How will you know whether the carbon dioxide has disappeared from the solutions in the test tubes?
When the carbon dioxide disappears, the BTB solution changes from yellow to blue.
4. If the carbon dioxide does disappear from the solutions in the test tubes, how will you know whether it was consumed by photosynthesis or simply evaporated into the air?
Greater loss of carbon dioxide from test tubes closer to the light and containing sprigs supports the idea that photosynthesis is removing the carbon dioxide.
5. How do you expect the intensity of light to affect the color of the
BTB indicator? Predict the result you expect for this experiment.
In test tubes that contain
Intensity on Photosynthesis
Introduction
Photosynthesis captures energy from sunlight. Plants, algae, and some bacteria use the energy captured during photosynthesis for their metabolic reactions. During photosynthesis in plants, chlorophyll and enzymes in leaves convert certain wavelengths of light into chemical energy. A simple equation can be used to represent photosynthesis.
Enzymes and Chlorophyll light energy CO2 H2O carbohydrate O2
In this investigation you will examine the relationship between the amount of light energy available and the rate of use of carbon dioxide by a plant in the process of photosynthesis.
Problem
What is the relationship between light intensity and the rate of photosynthesis? Pre-Lab Discussion
Read the entire investigation. Then, work with a partner to answer the following questions.
1. What are the variables in this experiment? Identify the manipulated and responding variables and two controlled variables.
The manipulated variable is light intensity. The responding variable is pH. Controlled variables include the initial pH, the size of the plant sprigs, and time.
2. How will you provide carbon dioxide to the evergreen sprigs?
Carbon dioxide is provided by blowing into the BTB solution.
3. How will you know whether the carbon dioxide has disappeared from the solutions in the test tubes?
When the carbon dioxide disappears, the BTB solution changes from yellow to blue.
4. If the carbon dioxide does disappear from the solutions in the test tubes, how will you know whether it was consumed by photosynthesis or simply evaporated into the air?
Greater loss of carbon dioxide from test tubes closer to the light and containing sprigs supports the idea that photosynthesis is removing the carbon dioxide.
5. How do you expect the intensity of light to affect the color of the
BTB indicator? Predict the result you expect for this experiment.
In test tubes that contain