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Trial 2 - Paper leaf versus living leaf

1. Imagine a large jar, like one that contained mayonnaise. Moist soil is put in. A healthy green plant is placed carefully in the soil. The lid is screwed on tightly. The plant receives sunlight and darkness in equal amounts. The temperature of the jar is maintained at 23 degrees Celsius or 75 degrees Fahrenheit. How long do you think the plant will live in the jar?

   

   
   
   
   

   A. It will die quickly.

   
   
   

   B. A few days.

   
   
   

   C. A few weeks.

   
   
   

   D. A month or more.

   
   
   Select one of the answers and explain your reasoning. Share and discuss your thoughts with other members of your group. After a few minutes, join others in your class that selected the same answer. Discuss your reasoning with this new group until you come up with a shared reasoning that you can use to defend your choice. Share your reasoning with the entire class.
   
   
   
2. The process of photosynthesis supplies food for plants by exchanging elements in the air and gathering energy.
   Identify some of the elements that are exchanged with the air by the leaves.
   
   What is the source of energy for the leaves?
   
   
   
3. If one were to look at the anatomy of a leaf, one could see how these elements are absorbed by the leaf so that they can form food. Leaves have a structure called a stoma by which this transfer of ingredients occurs. The stoma provides an opening to the inside of the leaf. These stomata (plural of stoma) are most numerous on the underside of the leaf. They can open and close, depending on the conditions. CO₂ (carbon dioxide) and H₂O (water) from the surrounding atmosphere are transported to and from the plant. Light shining on the leaf provides energy for the chemical reactions. The whole process of turning light energy into chemical energy for the plant is called photosynthesis.

   

4. Let's investigate the transfer of water through the stomata (plural of stoma). Select a healthy potted plant with broad leaves.
   
   
5. Use one of the leaves to trace a pattern of the leaf on construction paper. Be careful not to tear the leaf from the plant.

   

6. Carefully use scissors to cut out the pattern of the leaf.
   
   
7. Think about the differences you would see if you bagged both the paper leaf and a live leaf along with a relative humidity sensor. Would one of the bags show more signs of moisture than the other? Record your thoughts below.
   
   
   
   
8. Refer to Technical Hints to connect the relative humidity sensor. A relative humidity sensor will measure the amount of moisture in the air.
   
   
9. Place the paper leaf in a re-sealable bag with a relative humidity 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. Seal the bag and start the sensor. Refer to Technical Hints to record a series of measurements. Stop recording after about 1/2 hour. If you are not available to stop the data collection, arrange for someone else to stop the recording after 1/2 hour.

   

   
   
   
   
   
10. Place your plant near a window. Bag a live leaf while it is still on the plant with a relative humidity 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. Seal the bag around the stem and start the sensor. Refer to Technical Hints to record a series of measurements. Stop recording after about 1/2 hour. If you are not available to stop the data collection after 1/2 hour, arrange for someone else to stop the measurements.