1. Stomata & Transpiration Lab

2. Transpiration
The evaporation of water from a plant out of it’s leaves.
Plants LOSE water through transpiration (as it leaves through their stomata).

3. Plants GAIN water through their roots
Plants LOSE water through stomata in their leaves

7. Stomata can open & close
When might stomata spend more time open?
When might stomata need to spend more time closed?

8. What factors might affect transpiration rate?
In other words… what might affect how quickly or slowly water evaporates from a plant?

9. Based on the following table, is there a relationship between the habitat (in terms of moisture) to which plants are adapted and the density of stomata in their leaves?
Plant
Upper epidermis
Lower epidermis
Anacharis (water weed)
Black walnut
160
Corn 70 88
Water lily
460
Tomato 12
130

10. Transpiration Lab-Part 1
Determine a method for calculating leaf surface area
Make a wet-mount slide of a “nail polish stomata peel” to view a leaf epidermis (do each side of the leaf).

12. Transpiration Lab-Part 1
Draw & label what you observe
Count all the stomata in 1 microscopic field & record the #.
Do this for at least 3 microscopic fields to determine the average # of stomata/field

13. Transpiration Lab-part 2 Design your own investigation
Design a question to determine the effect of an environmental variable(s) on the rate of transpiration in plants. (Must be approved by me TODAY). See p. S142-S143 for basic setup.
Remember:
What’s the question being addressed?
What assumptions are being made & can those be verified?
Will the measurements you collect provide the data necessary to answer the question you are asking?
Did you include a control?
Materials:
Determine if all the materials you will need are available, or if lab group members need to bring additional materials tomorrow.
Be sure that at least 1 person from your group will be here tomorrow to set up the lab & that at least 1 person can collect the plant mass each day the rest of the week (think about AP test schedule).
Make a hypothesis about which environmental factors you think will have the greatest effect on transpiration rates