The Floating Leaf Disk Assay for Investigating Photosynthesis

Table of contents

Trying to find a good, quantitative procedure that students can use for exploring photosynthesis is a challenge. The standard procedures such as counting oxygen bubbles generated by an elodea stem tend to not be “student” proof or reliable. This is a particular problem if your laboratory instruction emphasizes student-generated questions. Over the years, I have found the floating leaf disk assay technique to be reliable and understandable to students. Once the students are familiar with the technique they can readily design experiments to answer their own questions about photosynthesis. The biology behind the prodedure: Leaf disks float, normally.

When the air spaces are infiltrated with solution the overall density of the leaf disk increases and the disk sinks. The infiltration solution includes a small amount of Sodium bicarbonate. Bicarbonate ion serves as the carbon source for photosynthesis. As photosynthesis proceeds oxygen is released into the interior of the leaf which changes the buoyancy–causing the disks to rise. Since cellular respiration is taking place at the same time, consuming oxygen, the rate that the disks rise is an indirect measurement of the net rate of photosynthesis.

Basis for leaf disk


  • Sodium bicarbonate (Baking soda)
  • Liquid SoapPlastic syringe (10 cc or larger)—remove any needle!
  • Leaf material
  • Hole punch
  • Plastic cups
  • Timer
  • Light source


  • Buffer Solutions
  • Colored Cellophane or filters
  • Leaf material of different ages
  • Variegated leaf material
  • Clear Nail polish


  • Prepare 300 ml of bicarbonate solution for each trial.
  • Prepare a 0. 2% solution. This is not very much it is only about 1/8 of a teaspoon of baking soda in 300 ml of water. )
  • Add 1 drop of dilute liquid soap to this solution. The soap wets the hydrophobic surface of the leaf allowing the solution to be drawn into the leaf. It’s difficult to quantify this since liquid soaps vary in concentration. Avoid suds.
  • If your solution generates suds then dilute it with more bicarbonate solution.
  • Cut 10 or more uniform leaf disks for each trial.
  • Single hole punches work well for this but stout plastic straws will work as well. Choice of the leaf material is perhaps the most critical aspect of this procedure. The leaf surface should be smooth and not too thick. Avoid plants with hairy leaves. Ivy, fresh spinach, Wisconsin Fast Plant cotyledons – all work well.
  • Ivy seems to provide very consistent results. Many different plant leaves work for this lab. My classes have found that in the spring, Pokeweed may be the best choice.
  • Avoid major veins.
  • Infiltrate the leaf disks with sodium bicarbonate solution.
  • Remove the piston or plunger and place the leaf disks into the syringe barrel.
  • Replace the plunger being careful not to crush the leaf disks.
  • Push on the plunger until only a small volume of air and leaf disk remain in the barrel (10%).
  • Pull a small volume of sodium bicarbonate solution into the syringe.
  • Tap the syringe to suspend the leaf disks in the solution.
  • Holding a finger over the syringe-opening, draw back on the plunger to create a vacuum.
  • Hold this vacuum for about 10 seconds. While holding the vacuum, swirl the leaf disks to suspend them in the solution. Let off the vacuum.
  • The bicarbonate solution will infiltrate the air spaces in the leaf causing the disks to sink.
  • You will probably have to repeat this procedure 2-3 times in order to get the disks to sink. If you have difficulty getting your disks to sink after about 3 evacuations, it is usually because there is not enough soap in the solution. Add a few more drops of soap.

Evacuating leaf disks Sunk

  • Pour the disks and solution into a clear plastic cup. Add bicarbonate solution to a depth of about 3 centimeters. Use the same depth for each trial.
  • Shallower depths work just as well.
  • For a control infiltrate leaf disks with a solution of only water with a drop of soap – no bicarbonate.
  • Place under the light source and start the timer. At the end of each minute, record the number of floating disks. Then swirl the disks to dislodge any that are stuck against the sides of the cups. Continue until all of the disks are floating.

Rising Data Collection and Analysis

These data are from an demonstration investigation using grape ivy leaf disks.

Graph The problem with ET50 is that it goes down as the rate of photosynthesis goes up–it is an inverse relationship and creates the following type of graph (data from Steucek, et al. 1985. ): InverseTo correct for this representation of the data and present a graph that shows increasing rates of photosynthesis with a positive slope the ET50 term can be modified by taking the inverse or 1/ET50.

Then I stirred the disks. Note that after a while the disks begin to sink. Why? Cellular respiration removes the oxygen from the cell spaces. The rate that the disks sink is an indirect measure of the rate of cellular respiration. Can you think of a way to how you might measure the gross rate of photosynthesis with this technique?


  1. Wickliff, J. L. and Chasson, R. M. 1964. Measurement of photosynthesis in plant tissues using bicarbonate solutions. Bioscience, 14: 32-33. Steucek, Guy L. Robert J. Hill and Class/Summer 1982.
  2. 1985. Photosynthesis I: An Assay Utilizing Leaf Disks. The American Biology Teacher, 47(2):96-99. Tatina, Robert E. 1986. Improvements to the Steucek and Hill Assay of Photosynthesis. The American Biology Teacher, 48(6): 364-366.
  3. Juliao, Fernando and Henry C. Butcher IV. 1989. Further Improvements to the Steucek and Hill Assay of Photosynthesis. The American Biology Teacher, 51(3): 174-176. Armstrong, Joeseph E. 1995.
  4. Investigation of Photosynthesis using the Floating Leaf Disk Assy. http://www. bio. ilstu. edu/Armstrong/biolab/cellbio/psynex1. htm Rukes, Kari L. and Timothy J.
  5. Mulkey. 1994. Measurement on the Effects of Light Quality and Other Factors on the Rate of Photosynthesis. Bioscene, 20(3): 7-11. ttp://www. acube. org/volume_20/v20-3p7-11.
  6. pdf Greenler, John. 1990. Exploring Photosynthesis with Fast Plants. WisconsinFast Plant Notes, 4(1): 4-5. http://www. fastplants. org/pdf/activities/exploring_photosynthesis.
  7. pdf BioPi listserv archives. http://listserv. ksu. edu/archives/biopi-l. html Enter the “Leaf Disks” for a search to review a thread on the technique. Dan Mott attached a copy of his lab using this technique to one of his postings. Richard, David S.
  8. Measure of Photosynthetic Rate In Spinach Leaf Disks http://www. susqu. edu/FacStaff/r/richard/photosynthlab. html

Calculate the price
Make an order in advance and get the best price
Pages (550 words)
*Price with a welcome 15% discount applied.
Pro tip: If you want to save more money and pay the lowest price, you need to set a more extended deadline.
We know how difficult it is to be a student these days. That's why our prices are one of the most affordable on the market, and there are no hidden fees.

Instead, we offer bonuses, discounts, and free services to make your experience outstanding.
How it works
Receive a 100% original paper that will pass Turnitin from a top essay writing service
step 1
Upload your instructions
Fill out the order form and provide paper details. You can even attach screenshots or add additional instructions later. If something is not clear or missing, the writer will contact you for clarification.
Pro service tips
How to get the most out of your experience with MyStudyWriters
One writer throughout the entire course
If you like the writer, you can hire them again. Just copy & paste their ID on the order form ("Preferred Writer's ID" field). This way, your vocabulary will be uniform, and the writer will be aware of your needs.
The same paper from different writers
You can order essay or any other work from two different writers to choose the best one or give another version to a friend. This can be done through the add-on "Same paper from another writer."
Copy of sources used by the writer
Our college essay writers work with ScienceDirect and other databases. They can send you articles or materials used in PDF or through screenshots. Just tick the "Copy of sources" field on the order form.
See why 20k+ students have chosen us as their sole writing assistance provider
Check out the latest reviews and opinions submitted by real customers worldwide and make an informed decision.
Business and administrative studies
Customer 452773, February 23rd, 2023
I just need some minor alterations. Thanks.
Customer 452547, February 10th, 2021
Great job
Customer 452773, February 13th, 2023
Business and administrative studies
excellent paper
Customer 452773, March 3rd, 2023
Don't really see any of sources I provided, but elsewise its great, thank you!
Customer 452697, May 8th, 2021
Business and administrative studies
Thank you
Customer 452773, March 19th, 2023
Looks great and appreciate the help.
Customer 452675, April 26th, 2021
10th grade English
very good
Customer 452773, March 26th, 2023
Business and administrative studies
great job as always
Customer 452773, February 26th, 2023
Thank you!!! I received my order in record timing.
Customer 452551, February 9th, 2021
Criminal Justice
The paper was not accused of plagiarism and was written very well. I will let you know the grade once it is graded. Thank you
Customer 452671, April 26th, 2021
Business and administrative studies
excellent work
Customer 452773, March 9th, 2023
Customer reviews in total
Current satisfaction rate
3 pages
Average paper length
Customers referred by a friend
15% OFF your first order
Use a coupon FIRST15 and enjoy expert help with any task at the most affordable price.
Claim my 15% OFF Order in Chat

Sometimes it is hard to do all the work on your own

Let us help you get a good grade on your paper. Get professional help and free up your time for more important courses. Let us handle your;

  • Dissertations and Thesis
  • Essays
  • All Assignments

  • Research papers
  • Terms Papers
  • Online Classes



eskişehir eskort



eskişehir eskort

Live ChatWhatsApp