Name _______________________________________________ Date ___________________ Period _______
Stomata Lab
PRE-LAB:
Stomata are openings or pores on leaf surfaces that allow plants to take in CO2 from the atmosphere, which is necessary
for photosynthesis. Plants also lose water through stomata by transpiration. One way that plants can minimize water loss (or
maintain water homeostasis) while acquiring CO2 is to regulate the number of stomata on the upper and lower surfaces of
their leaves. In this lab you will compare stomatal densities on upper and lower leaf surfaces.
PART A: Form a hypothesis
Answer the following questions based on the information presented before the lab.
1. What tradeoff do plants have to address that may affect stomatal density on one side of a leaf vs. the other side?
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2. List at least one potential advantage or disadvantage of having more stomata on the upper and lower side of the leaf
(hint: think of a hot, sunny day):
Upper side of the leaf: ____________________________________________________________________________
Lower side of the leaf: ____________________________________________________________________________
Based on this knowledge, which leaf surface do you think will have more stomata? Why?
Form a hypothesis answering these questions.
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PART B: Make stomata peels and collect data
Using the instructions provided, prepare a slide with a peel from the upper surface of a leaf and the lower surface of a leaf to
fill in the table below.
Table 1.1 Number of stomata on upper and lower leaf surfaces. Report your average number of stomata from the
upper and lower leaf surfaces to your teacher.
Figure 1.1 Draw and label stomata and leaf cells of the lower leaf surface as you see them in your field of view. Be
sure to label the stomata and guard cells of at least one unit you see.
PART C: Conclusion
1. Based on the class’s data, was your hypothesis supported or rejected? Explain.
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2. The stomata open & close in response to pressure within what
cells? ________________
What are the 3 main functions of leaves?
3. _______________________, 4. ______________________, &
5. ___________________________
6. During gas exchange plants take in _____________ and they
release _____________
7. The exchange of these gases takes place through tiny holes in
the leaf called ________________.
8. xylem - carries ___________ which travels from the
_______________ to the _______________
9. phloem - carries ___________ which travels from the
______________ to the _______________
10. When plants lose water through their leaves, this process is called _________________________________.
PART D: LEAF ANATOMY AND PHOTOSYNTHESIS OVERVIEW
1. What are the reactants for photosynthesis? _________________________________________________________
2. Where do these reactants enter the leaf? ___________________________________________________________
3. What are the products of photosynthesis? __________________________________________________________
4. From where do the products leave the leaf? ________________________________________________________
5. Write the equation for Photosynthesis: _____________________________________________________________
6. Plants that live on the floor of forests tend to have much larger leaves than plants than live in hot, sunny conditions.
Offer an explanation for this in which you refer to specific parts of the internal structure of a leaf.
7. Cacti are plants that live in extremely dry environments. Unlike most other plants, cacti do not have regular leaves,
but instead have spines. They do have green stems. How would the lack of regular leaves help cacti survive in their
environment? In what part of the cacti would photosynthesis occur?
8. Circle the tropism that leaves react to. Underline the tropism roots react to. Box the tropism vines use to grow up houses.
Gravitropism
Thigmotropism
Phototropism