Photosynthesis Leaf Disk lab 2020-2021 PDF

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Download Photosynthesis Leaf Disk lab 2020-2021 PDF

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Name __________________________

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Inv Investigating estigating Photosynthesis - Th The e Floating Leaf Disk Ass Assay ay 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 water, Sodium bicarbonate (NaHCO3) and some soap. Materials: Bicarbonate/Soap Solution, syringe, spinach leaves, straw or hole punch, beakers/cups, timer, light source, aluminum foil (use to cover your setups until you are ready to begin) Procedure: 1. Fill a small beaker or cup with 0.2% bicarbonate solution. Add 1 tiny drop of soap to your mixture. The soap wets the hydrophobic surface of the leaf allowing the solution to be drawn into the leaf.

2. Cut 10 uniform leaf disks from the spinach for each trial. o Use a single hole punch. o Avoid major veins on leaves o What about your control? What are you testing here? You will need to create a control group for this experiment. Write it below before you proceed. ______________________________________ ______________________________________

3. Infiltrate the leaf disks with sodium bicarbonate solution. Directions follow below: o Remove the piston or plunger and place the leaf disks into the syringe barrel. o Replace the plunger being careful not to crush the leaf disks. Push on the plunger until only 1mL of air and leaf disk remain in the barrel. o Pull sodium bicarbonate solution into the syringe. Tap the syringe to suspend the leaf disks in the solution. o 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. Adapted by SJackson and SGood from Brad Williamson http://www.elbiology.com/labtools/Leafdisk.html

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o Push the plunger back up and then remove your finger from the top to 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. You may have to flick the syringe several times. Do not repeat more than 3 times or you will need new leaf disks!

4. Pour the disks and solution into the solution remaining in the beaker, cover with aluminum foil. 5. Prepare the control group. 6. Place under the light source and start the timer. o At the end of each minute, record the number of floating disks for the active group and your control. o Be sure to collect the data in a systematic way. You will eventually need to present the data in a table. o Then swirl the disks to dislodge any that are stuck against the sides of the beakers. Continue until all of the disks are floating.

Adapted by SJackson and SGood from Brad Williamson http://www.elbiology.com/labtools/Leafdisk.html

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1. What is your control?

2. What is your hypothesis?

3. Please create a data table for your results and attach it to the report. 4. Graph your results below on the graph paper provided at the end of the report. Your graph should have number of disks floating vs. time. What is your dependent variable?___________________________

What is your independent variable?___________________________

5. What gasses are being exchanged and how do they affect the buoyancy of the leaf? Explain.

Adapted by SJackson and SGood from Brad Williamson http://www.elbiology.com/labtools/Leafdisk.html

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6. The leaf disks are suspended in water, baking soda and soap. Why do we add baking soda?

7. What happens when you put the leaf disks under the light? Why? Please give a detailed explanation.

8. After you have mastered the floating disk technique, you will design an experiment to test another variable that might affect the rate of photosynthesis. Explain the basics of your experiment below. What variable would you test? Briefly describe the materials and methods as well as your hypothesis.

Adapted by SJackson and SGood from Brad Williamson http://www.elbiology.com/labtools/Leafdisk.html

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Adapted by SJackson and SGood from Brad Williamson http://www.elbiology.com/labtools/Leafdisk.html...