Measuring Rate of Photosynthesis
In this lab, students will apply their knowledge and curiosity to explore how important sunlight and carbon dioxide is to photosynthesis. Because I do not have high school biology experiences, I would like to thank Brad Williamson from Explore Life Community for posting great instructions and photos! Please visit his web page for more biology teaching resources
- Sodium bicarbonate (baking soda)
- Plastic syringe
- Fresh spinach leaves
- Hole punch
- Plastic cups
- Light Source
- Prepare a 0.2% sodium bicarbonate solution
- Add one drop of liquid soap to this solution
- Using the hole-puncher, cut out 10 or more spinach leaf disks
- Put discs in syringe and suck up 5 mL of the bicarbonate solution
- Put finger over end of syringe, pull back on plunger to about halfway and hold this position for 30 seconds. At this point, the oxygen in the spongy layer of the leaf is being replaced by the sodium bicarbonate solution. This is the plant's source of carbon dioxide
- Repeat this procedure 2-3 times until the leaf disks sink. If you have difficulty getting your disks to sink after about 3 tries, I would recommend add more soap.
- Eject the content of the syringe (discs and bicarbonate solution) into a clear plastic cup. Add bicarbonate solution to a syringe depth of about 3 centimeters. Stay consistent with the depth for each trail
- Infiltrate some leaf disks with a solution of only water with a drop of soap--no bicarbonate
- Place plastic cups under the light source and start the timer. At the end of each minute, record the number of floating disks. Remember to swirl the disks to dislodge any that are stuck against the sides of the cups. Continue until all of the disks are floating.
- Which conditions are most effect in getting leaf discs to float?
- Goggles should be provided to students
- Wipe up spills immediately to prevent students from slipping and falling
- Take precaution when handling sodium bicarbonate