- The Effect Of Carbon Dioxide On The Rate Of Photosynthesis 6co 6h 0 Light Energy C H O 60 As The Chemical Equat 1 (66.33 KiB) Viewed 9 times
- The Effect Of Carbon Dioxide On The Rate Of Photosynthesis 6co 6h 0 Light Energy C H O 60 As The Chemical Equat 2 (45.03 KiB) Viewed 9 times
The Effect of Carbon Dioxide on the Rate of Photosynthesis 6CO, + 6H,0 + light energy C,H,O, + 60, As the chemical equation above indicates, plants require light, carbon dioxide, and water to carry out photosynthesis. If any of these substances are not present or the concentrations are reduced, the rate of photosynthesis should be affected. Because a leaf's spongy mesophyll normally contains the gases O, and CO₂, they normally float when put into water. If the gases are removed using a vacuum and replaced with water and sodium bicarbonate, NaHCO,, then the density of the leaf should increase, and the leaf will sink. Sodium bicarbonate, NaHCO,, provides the carbon dioxide plants require for photosynthesis. In this experiment you will examine how the presence or absence of carbon dioxide affects the rate of photosynthesis by spinach leaves. The rate of photosynthesis can be determined by measuring one of the end products. In this exercise you will be measuring oxygen, which is produced during the light-dependent reactions. As the spinach leaves photosynthesize, they should begin to produce oxygen, which in this experiment should cause them to rise. 1 Procedure 8.2 Measuring the Effect of Carbon Dioxide on Photosynthesis 1. Obtain a ring stand, lamp, test tube rack, and fish bowl. Anchor the lamp to the ring stand, making sure not to turn the lamp on. Next, fill the fish bowl with cold water. 2. Position the fish bowl of cold water between the lamp on the ring stand and the test tube rack. 96 3. Obtain a hole punch, two syringes, wax pencil, and 2-3 spinach leaves. 4. 5. Using a hole punch, cut 20 uniform leaf disks from 2-3 spinach leaves. Avoid major leaf veins. Using a wax pencil, label the 1st syringe as water and the 2nd syringe NaHCO, (sodium bicarbonate). 6. Remove the plunger from each syringe and, using forceps, carefully place 10 leaf disks into each syringe. Gently tap the syringe on the bench until all leaf disks settle into the bottom (tip region) of the syringe. 7. Gently reinsert the plunger into the syringe, making sure not to crush the leaf disks. 8. Obtain two beakers and label the first water and the second 5% NaHCO,. Place 15 mL of water in the first beaker and 15 mL of 5% NaHCO, in the other. Photosynthesis Laboratory 8
9. Draw up 10 mL of water into the water-labeled syringe. 10. Next, place your thumb tightly over the tip of the syringe in order to create a seal. With the syringe pointed down, slowly draw back the plunger as far as it will go without pulling the plunger out WHILE keeping your thumb tightly sealed over the tip. Holding the syringe with the tip down, shake the syringe in this position for 15 seconds. This creates a vacuum and draws the air out of the leaf disks. 11. Release the plunger, automatically moving the plunger back into the syringe. Gently tap the syringe to dislodge any disks that may have stuck to the sides of the syringe. 12. Some air may have accumulated in the tip. Slowly push the plunger in to remove the air in the tip of the syringe. Let the syringe sit with the tip pointed up for 30 accumulated seconds. 13. Repeat steps 10-12 until no more than two leaf disks remain floating at the top of the syringe (tip end). 14. Place the water-labeled syringe in a test tube rack with the tip up and remove your thumb. 15. Repeat steps 10-14 using the 5% NaHCO, (sodium bicarbonate) solution. 16. Once both syringes have been placed in the test tube rack with the tips pointed up, turn on the lamp and start the timer. At the end of each minute, gently tap each syringe to dislodge. any disks that may have stuck to the sides of the syringe. After 10 minutes, count how many disks have risen to the top of the syringe. 881 Figure 8.2: Basic setup for measuring the effect of carbon dioxide concentration on photosynthesis. 6 NaHCO, 0 5 Obluedoor, LLC Table 8.1: The effect of carbon dioxide concentration on the rate of photosynthesis. Number of Leaf Disks to Rise after 10 Minutes Group Data Class Average Laboratory & Photosynthesis 97