Effects of Light Intensity and Carbon Dioxide on Photosynthesis

This experiment uses the floating disk leaf assay as a tool for exploring the process of photosynthesis in plants. As the process of photosynthesis proceeds, a significant amount of oxygen is released from the outside of the leaf forming bubbles. This alters the buoyancy causing the disks to rise. The rate at which the disk rises is and indirect measure of the net rate at which oxygen is produced as the process of photosynthesis is taking place. The Bicarbonate ions in the solution serve as the source of carbon required for photosynthesis

Is your time best spent reading someone else’s essay? Get a 100% original essay FROM A CERTIFIED WRITER!

Save 25%

Materials

Sodium Bicarbonate (baking soda)

Liquid Soap

Syringe

A green leaf

Hole Punch

Timer

Light Source (Compact Fluorescent/In cadence)

Stir sticks

Plastic cups

Beakers

Tin foil

Method

Start by labeling four plastic cups as follows

20 cm CO2 light

10 cm CO2 light

10 cm Water/ soap light

CO2 Dark

Have the two beakers labeled A and B

Take 300 ml of bicarbonate solution and put it in beaker A

To the bicarbonate solution in beaker A, add a 300 ml of water and stir.

Put 300ml of water in beaker B and add 200ml of soap solution as you stir

To beaker A, add a drop of soap solution and continue stirring as well

Hole punch 30 complete leaf disks in texture and thickness

Take out the plunger of the syringe and position ten leaf disks in the syringe barrel

Replace the plunger carefully so as to avoid crushing the leaf disk.

Draw a small amount of the infiltrate solution into the syringe from beaker A. Invert the syringe and tap the syringe to spread the leaf disks inside the infiltrate solution.

Push the plunger while drawing away as much air as you can from the syringe.

Place a finger over the syringe opening channel and draw the air.

Pour the disks and the bicarbonate solution into a marked cup

Add the infiltrate solution from beaker A until almost the cup is half full

For the first trail (the first cup named cup in step one) put the light exactly 20cm below the top of the stand. For the second and third place the light 10 cm below.

Start the timing just after exposing the leaf disks to the light

Discussion

When the leaf is exposed to light, the leaf starts to produce oxygen. As the process of photosynthesis proceeds, a significant amount of oxygen is released from the outside of the leaf forming bubbles. This alters the buoyancy causing the disks to rise. When these leaf intercellular spaces are otherwise occupied with the solution, the density of the leaf rises making the leaf to sinks. Penetrating the air spaces with the bicarbonate solution, which includes a little amount of Sodium bicarbonate, makes the total mass of the leaf disk to increases causing the disk to sink. Since the rate at which the disk rises is and indirect measure of the net rate at which oxygen is produced as the process of photosynthesis is taking place. The leaf in trial 1 sunk faster indicating that the more the light, the higher the rate of photosynthesis.

Conclusion

The rate of photosynthesis is seen to be higher when both the amount of carbon dioxide and sunlight are high.