Investigating Photosynthesis Using A Floating Leaf Disk Assay



Investigating Factors that Affect the Rate of Photosynthesis Using A Floating Leaf Disk Assay

Introduction

Photosynthesis is the metabolic process used by all autotrophs to capture light energy and convert it to the chemical energy of carbohydrates and other organic molecules. What are factors that can affect the rate at which this process occurs? Although numerous intermediary reactions are involved, the overall photosynthetic reaction is simple: Carbon dioxide combines with the hydrogen from water yielding a carbohydrate—the 6-carbon sugar glucose—and oxygen gas.

The photosynthetic production of oxygen and our knowledge of leaf anatomy allow us to construct a system that can be used to experimentally investigate many of the photosynthetic variables. Many extracellular spaces exist within plant leaves that are normally filled with air for purposes of gas exchange. This is why leaves will float on the surface of bodies of water. But what would happen if all the air is forced out of the air spaces in the leaf? What will the leaf do then?

Using small disks cut from leaves rather than a whole leaf to perform the floating leaf disk assay (FLDA), you will investigate factors not previously tested in class and determine how they may affect the photosynthetic rate. Using the experimental design map on the next page, outline the procedure you will follow in order to test the variable you choose. This will be graded using the Design criteria for internal assessments. Your teacher must approve your experimental design map before you can begin testing your experiment.

Any data you collect from the prescribed experiment you perform will be graded using the Data Collection and Processing criteria for internal assessments.

You will write a conclusion and data analysis about this lab activity, and it will be graded using the Conclusion and Evaluation criteria for internal assessments.

Be sure to use the IA grading criteria to guide your work! Grading will be much more stringent now that you have been in class for almost an entire school year!

References:

Armstrong, Joseph E. (1995) Investigation of Photosynthesis using the Floating Leaf Disk Assay.



Richard, David S. Measure of Photosynthetic Rate In Spinach Leaf Disks.

Williamson, Brad. Measuring the Rate of Photosynthesis with the Floating Leaf Disk Assay.

Experimental Design Map:

You must have teacher approval before you start experimentation.

Research Question: What do you want to know?

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Independent variable: What experimental factor will you change to produce an outcome? What levels of treatment will you use?

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Dependent variable: What will you measure? Will you collect quantitative data or qualitative data?

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Hypothesis: What is your proposed solution (educated guess) to the problem?

Control group: What kind of control group will you establish as a standard for comparison?

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Constants: What conditions will you keep constant?

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Materials and Equipment: Choose materials from the list your teacher will provide and list them here.

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Experimental Set-Up: make a diagram of what you think your experimental setup will look like. When you turn in your final report, you may need to make adjustments to this.

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Safety considerations: what safety precautions will you take?

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Procedure: write your proposed procedure here. When you turn in your final report, you may make modifications to your actual procedure, but use this as your reference.

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Teacher Initials for Approval

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