Photosynthesis Stations

Light or Dark?• Bromothymol Blue is an indicator that is blue in the

presence of O2, and turns yellow/light green in the presence of CO2.

• Observe all the test tubes.• Observe the tubes placed in the dark for 48 hrs.1) Why do you think all of the tubes, except one, are still

yellow, even in the presence of plants?• Observe the tubes exposed to sunlight for 48 hours.2) Why do you think one out of the 4 tubes is still yellow?3) What is the snail releasing that is keeping the tube yellow?4) What is the plant releasing that is keeping the tube blue?

CO2Reactant or Product of Photosynthesis?

• Fill empty flask with 150 ml’s of water.• Please be sure everyone in the groups is wearing an apron!• Put about 20 drops of bromothymol blue indicator into

flask• One person in the group, put on goggles, take a clean

straw, mix the blue thoroughly in water.• Compare the flask you just mixed to the control. They

should be the same color.• Now blow through the straw and observe what happens.1) What happened to color when blowing into the straw?2) What molecule are you blowing out that caused the color

change?

Stomata• Observe the underside of leaf under the

microscope• Notice the stomata (openings).• These openings (stomata) are the little “mouths”

that the plant uses to “breathe”.1) What gas does the plant breathe in?2) What gas does the plant breathe out?The stomata are closed at night.3) Why do you think they are open during the day?

Veins• Observe the top of leaf under the microscope.• Notice the veins (bright lines running through it)• Observe the leaf samples, do they have veins?1) What does the plant need that travels through

these veins?2) What is the name of the bundle of tubes within

the veins that carry H2O to the cells (pg.181 last paragraph)

3) How are these veins similar to ours?

Leaf Cross-Section• Observe the cross-sections of the leaf.1) What energy source is hitting the top of the leaf?• Notice the location of the chloroplasts2) What important process takes place in the chloroplasts?3) In what layer of the leaf do you think most of the photosynthesis occurs?

The Carbon and Oxygen Cycle

• Analyze the Carbon and Oxygen Cycle1) What is the energy driving the cycle?2) What are 3 ways in which CO2 is released into

the air?3) What are 2 ways in which Carbon is absorbed

into the ground?4) What process is recycling the CO2 into O2?