NAME______________

PERIOD______________

DATE______________

LAB GROUP #______________

STOMATA LAB

INTRODUCTION

In this lab, you will be looking at the stomata from three different leaves. You will work with your lab group to prepare samples, view the stomata, and draw conclusions about the environment that these plants grew in and evolved in. Before you begin, you will need to write a hypothesis and decide how you will collect and analyze data.

PRE-LAB QUESTIONS

What is density? What is the formula used to describe the stomatal density of a leaf? (Hint: if you are not sure, look at your reading)

Density = mass/volume

Stomatal Density = stomata/area

What information will your group need to collect so that you can calculate stomatal density?

Our group will need to find the area in single scope view and number of stomata in a single scope view for each leaf. We will count the number of stomata in three single scope views for each leaf.

Question: Choose a question to answer.

□ How does the position of the leaf on the tree affect stomatal density? (you will sample leaves from one tree)

□ How does leaf size affect stomatal density? (you will sample leaves from one tree)

□ How does the stomatal density of the leaves on three different trees compare?

Hypothesis: Write your hypothesis here.

Ex 1. The smaller leaf the lower the stomatal density will be. The larger the leaf the higher the stomatal density will be.

Ex 2. The shiniest leaf will have the highest stomatal density. The least shiny leaf will have the lowest stomatal density.

Procedures:

1. Follow your teacher’s instructions for gathering different leaves. 2. Brush the underside (the dull side) of one of your leaves with nail polish. Allow the nail polish to

dry completely. 3. Apply a piece of tape to the patch of dried nail polish. 4. Gently peel the tape off of the leaf. The nail polish should come off of the leaf and be stuck on

the tape.5. Press the tape onto a microscope slide. Label the slides. 6. Use 40x magnification to view the stomata of the leaf. Count the stomata within your field of

view for each leaf.

Results: Create a table below to record your data.

Sample 1

Leave height on tree

# stomata leaf 1

# stomata leaf 2

# stomata leaf 3

Average number of stomata

Stomatal density

4 feet6 feet8 feet

Sample 2

Tree # stomata leaf 1

# stomata leaf 2

# stomata leaf 3

Average number of stomata

Stomatal density

AcaciaMesquite

Conclusions:

Restatement of purpose

Summary of procedures and findings

Conclusion: was the hypothesis correct or incorrect

Possible sources of error (procedural errors, measurement errors, sample size, ect)

Future investigations

Sample conclusion:

The purpose of this study was to investigate the relationship between tree height and stomatal density. Mesquite leaves from various heights were sampled. On average, leaves taken from 4 feet off of the ground had a stomatal density of ____, leaves from 6 feet off of the ground had a stomatal density of ______, and leaves from 8 feet off of the ground had a stomatal density of _______. The results indicate that the hypothesis was correct; the position of leaves on trees affects (or does not affect) the stomatal density. The higher leaves are on trees, the ______________ the stomatal density. Small sample size may have affected results. Future studies should include a larger sample size in order to strengthen the findings.

Assessing Your Learning

1. Describe the differences between the stomata of the different leaves.

Ex. The stomata of the grass seemed long and had thick ends like dumbbells. The stomata of the oak tree were shaped more like kidney beans. In addition the stomata of the grass were larger than the stomata of the grass.

2. Which leaf do you think is best adapted to the desert? Why?

I think the leaf with the lowest stomatal density is best adapted to the desert. A plant in a wet area would evolve to have many stomata so that it can release a lot of water. A plant in a dry area would need to conserve its water. It would have fewer stomata so that it would not transpire as much water.

3. How would you expect the stomata of a leaf respond to a drought? What about a flood? Why?

In a drought the stomata would close so that less water would be lost to transpiration. By doing this the plant would produce less food, but be able to prevent drying out irreparably. Conversely, in a flood a plant would open its stomata so that it could transpire as much water as possible. This would allow it to deplete the water surrounding its roots so that it can access oxygen and so that the roots do not rot.

4. What factors other than water would affect whether stomata are open or closed?

Stomata are used by plants to intake CO2 through their stomata. CO2 is required for plants to produce food. Sometimes plants must open their stomata to take in CO2 even if it puts them at risk of losing too much water.

5. Why would a scientist be interested in studying stomata? What do you think a scientist could tell about the environment based on stomata?

A scientist could learn about the type of environment that a tree is adapted to by looking at stomata. They also might be able to learn about recent weather conditions in an area based on what stomata are doing. If a scientist wanted to understand how much water an ecosystem is transpiring, they might be able to estimate transpiration based on stomatal density.