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Trial 2 - 24-hour cycle of bagged leaves

1. Again, select a healthy potted plant with broad leaves.

2. Remember the stomata openings. In a way, this is how the plant breathes and exchanges gases like we do. In light guard cells around the opening swell, causing the pore to be at its widest, and CO₂ (carbon dioxide gas) spreads into the leaf and into the cells to be used in photosynthesis. In the dark or under drought conditions the guard cells are closed and no photosynthesis takes place. Opening of the stomata not only allows CO₂ to diffuse into the leaf, but allows water vapor to diffuse out of the leaf. The release of water from leaves through their stomata is called transpiration.

   

   What different conditions will cause the stomata to open or change size?
   
   
3. Think about the differences you would see on your graphs if you bagged a living leaf with a relative humidity sensor and light sensor for 24 hours. Would the graph show signs of moisture changes with the varying amounts of light? Record your thoughts.
   
   

4. Divide your class in two different groups for testing. One type of testers will bag a paper leaf with a relative humidity sensor and a light sensor for 24 hours. The other type of testers will bag a living leaf with a relative humidity sensor and a light sensor for 24 hours.

5. Refer to Technical Hints to connect the relative humidity sensor.

6. Refer to Technical Hints to connect the light sensor.

7. If you are one of the paper leaf testers, bag your paper leaf from Trial I with a relative humidity sensor and a light sensor. Make sure the slots on the relative humidity sensor are not blocked and are open to the air in the bag by standing the sensor on one end. Also, make sure the tip of the light sensor is not blocked. Seal the bag and start both sensors. Refer to Technical Hints to record a series of measurements. Stop recording after 24 hours.

   

   
   
   
8. If you are one of the living leaf testers, place your plant near a window. Bag a living leaf while it is still on the plant with a relative humidity sensor and a light sensor. Make sure the slots on the relative humidity sensor are not blocked and are open to the air in the bag by standing the sensor on one end. Also, make sure the tip of the light sensor is not blocked. Seal the bag and start both sensors. Refer to Technical Hints to record a series of measurements. Stop recording after 24 hours.

   ***Missing Image lightandrelativehumiditylive.jpg***