Download Lab.Stomata

Name: _____________________________________________________
Activity: Stomata in Leaves
Goal: To observe stomata and guard cells in plant tissue and
describe their function.
Background Information: Photosynthesis is the process plants use to make
food. The chemical reaction for photosynthesis requires two raw materials; they
are carbon dioxide and water. The sunlight that is captured by the chlorophyll
helps the chemical reaction take place. The chlorophyll is contained in the
chloroplasts of plants.
In plants, the roots absorb water from the soil. The water then moves up
through the plant stem to the leaves. Carbon dioxide is one of the gases in the
air. It enters the plant through small openings on the undersides of the leaves
called stomata. Guard cells control the stomata and therefore regulate the
movement of gases, especially water vapor and carbon dioxide, into and out of
leaf tissues. A stoma opens or closes in response to the changes in pressure
within the guard cells that surround the opening. When the guard cells are
swollen with water, the stoma is open. When the guard cells lose water, the
opening closes. Plants regulate opening and closing of the stomata to balance
water loss with rates of photosynthesis.
Materials: Iodine, lettuce leaf, water, microscope slide, cover slip, microscope,
professionally prepared slides (Epidermis Leaf, 93 W 1020)
Procedure:
1. What I Know: Write two sentences describing what you already know about
what materials need to move into and out of plant cells during photosynthesis?
How do you think they enter the cell?




Observe a prepared slide. If this is not available obtain a small piece of
lettuce. Using a crisp section of the leaf, bend the leaf and gently pull away
the epidermis. This is a thin transparent tissue on the underside of the leaf.
Make a wet mount of the epidermis using fresh water.
Focus your specimen under low power (40X), and then switch to 100X.
Scan your specimen for stomata and guard cells.
2.What I Observed: Draw a leaf section, label a stoma and the guard cells. Write
a detailed caption of your observation.
Caption:
Plant Cell
____X
3.What I Wonder: Pose a why or how question you may still have concerning
stomata or guard cells.
4.Questions: Write the answers to the following questions using complete
statements.
a. Describe the shape of the guard cells around the stomata.
b. What is the function of stomata in a leaf?
c. What evidence did you see that shows guard cells engage in
photosynthesis?
d. What substance or substances do you think enter or leave the leaf
through stomata?
5.Claim and Evidence Writing Prompts: Use the following prompts to help
you construct your lab conclusion, What I Learned.
 Goal: State the goal of this lesson.
 Claim: What did you learn from the activity that satisfies the goal of
this lesson? This is an I Learned statement.
 Evidence: How can you prove from your observations that you
learned what you claim? This can be a general statement that you
will explain in detail in your explanation.
 Explanation: Use specific data from your observations to support
your claim and describe the evidence.
 Concluding Statement: Reword the goal and either add
information you learned about the topic from your text book, class
discussions, and/ or personal research OR you can extend the
statement by adding a relevant question.
6. What I Learned: Write at least one paragraph describing what you learned
from this activity. Be sure to use the lab rubric and to use the writing prompts that
include goal, claim, evidence, explanation and concluding statement.