Below: Figure 1 Photosynthesis

Would you like your students to discover what really happens to gas levels during respiration and photosynthesis? The CO2 -O2 Tee (order code CO2-TEE, $5) now makes this possible. The CO2 -O2 Tee can be used with a CO2 Gas Sensor and an O2 Gas Sensor to monitor gaseous carbon dioxide and oxygen levels simultaneously in a closed system. The Tee is designed to fit snugly into the neck of the 250-mL Nalgene bottle that ships with both sensors, as shown in Figure 1. With the bottle on its side and the tapered end of the Tee inserted into the bottle, the O2 Gas Sensor fits into the top opening of the Tee while the CO2 Gas Sensor fits into the opening directly across from the bottle.

For an easy, yet elegant, photosynthesis/respiration experiment, put some leaves or small plants into the Nalgene bottle and set up a round, 30-W, fluorescent light, as shown in Figure 1. The data in Figure 2 was taken with eight Wisconsin Fast Plant seedlings planted in a 50/50 mixture of vermiculite and peat. The seedlings were one week old. Initially, the bottle was wrapped in aluminum foil so that the plants were in the dark. The aluminum foil was then removed and the light turned on to allow photosynthesis to occur. This can also be done with fresh-cut spinach leaves, as shown in Figure 1.

Figure 2

An experiment file for monitoring both gas levels simultaneously is available in Logger Pro 2.1.1 in the CO2 Gas Sensor or the Oxygen Gas Sensor folder. The file is called CO2 & O2.mbl.