Name: _______________________
Earth Science
Date: ___________
Block: ___________
Ozone and Milkweed Lab
Objectives:
Students will
1) observe signs of ozone plant damage,
2) determine the severity of ozone damage to individual plants and plant
communities.
Background
Did you know that plants and animals can give us clues about pollution
in our air, land, and water, before humans even notice that something is
wrong? Even lichens and birds can tell us about air quality. Bio-monitoring is
the term scientists use to describe this use of plants, animals, or entire
ecosystems to tell if our environment is polluted. These techniques have
been used by biologists and scientists to give us information about our
surroundings for a long time.
Common milkweed is a good plant to study for signs of pollution
because it is affected by ozone and it grows in a lot of areas. Students will
be environmental doctors and conduct a simple milkweed check-up for ozone
damage. Ozone injury on milkweed can be seen on the leaves. This injury is
unique and is pretty easy to identify. As plant doctors, students can look for
these symptoms: sharply defined, small dot-like lesions, called stipples, on
the top (upper surface) of the leaves. These markings appear only on the
top of the leaf and are black to dark purple. If the ozone effects are severe
you'll see a large dark area on the upper leaf surface as the markings blend
together.
Ozone injury can look different on leaves of different ages. Minor
ozone injury on young leaves can be found on the tip of the leaf. It is found
in the center of fully grown leaves and at the base of older leaves. Leaves
that are exposed to lots of ozone may show injury symptoms all over the
upper leaf surface. You and your students can view a slide show of ozone
and other damage to milkweed leaves to help you in your studies.
Materials





worksheet
pencil
clipboard
milkweed plants
ruler
Name: _______________________
Earth Science
Date: ___________
Block: ___________
Standards
New York State
STANDARD 1—Analysis, Inquiry, and Design
Students will use mathematical analysis, scientific inquiry, and engineering design, as appropriate, to
pose questions, seek answers, and develop solutions.
STANDARD 6—Interconnectedness: Common Themes
Students will understand the relationships and common themes that connect mathematics, science, and
technology and apply the themes to these and other areas of learning.
STANDARD 7—Interdisciplinary Problem Solving
Students will apply the knowledge and thinking skills of mathematics, science, and technology to address
real-life problems and make informed decisions.
2.2d Temperature and precipitation patterns are altered by human influences including deforestation,
urbanization, and the production of greenhouse gases such as carbon dioxide and methane.
Problem or Question
State the problem or question you are investigating for this experiment.
_____________________________________________________________
Hypothesis
Make a hypothesis of how much damage there will be due to ozone. Give
percent of injured leaves or number of damages leaves.
_____________________________________________________________
_____________________________________________________________
Control Group - _______________________________________
Experimental Group - ___________________________________
Dependent Variable - ___________________________________
Independent Variable - _________________________________
Procedure
1. In your assigned group, obtain two milkweed plants from your teacher.
Decide where you want to put your plants. Plants can be 50 feet from
the road. Plants can be in the classroom. Plants can be outside the
classroom window.
2. Have students select milkweed plants to conduct the check-up
everyday for a week.
Name: _______________________
Earth Science
Date: ___________
Block: ___________
a. Have students choose 10 stems at random for the study. Each plant
must have a stem with 10 or more leaves on it. Have students avoid
plants that are diseased or have insect chewing marks on them.
b. Have students draw a map showing the location of the study area.
Show features near the site like roads, trails, signs and buildings that
would allow another person to easily find the site.
c. Have students use the chart below to record their findings.
3. Have students conduct the check up.
a. Students should select their first milkweed stem and measure and record
the height of the stem from the base to the top. Have students use
centimeters for their measurement and record this on the chart.
b. Students should count and record the number of leaves showing ozone
injury on the plant (see the picture to identify leaf injury).
c. Have students estimate the percentage of leaf area injured using the
following code:
Name: _______________________
Earth Science
Date: ___________
Block: ___________
Code % of leaf area injured
0
no visible signs of injury
1
very light to some (1-15%)
2
moderate to moderately heavy (16-50%)
3
heavy (more than 50%)
d. Have students count and record the number of leaves showing ozone
injury on the plant.
4. They should also record the total number of leaves on the plant. Have
them evaluate only mature leaves that measure 5-10 centimeters in
length. Students should then determine the percentage of injured
leaves per plant using the guide above. Have them complete all 10
plant check-ups.
Plant
Number
1
2
3
4
5
Plant
Height
Total #
Leaves
#
Injured
Leaves
%
Injured
Leaves
on Plant
% Leaf
Area
Injured
Name: _______________________
Earth Science
Date: ___________
Block: ___________
6
7
Evaluation
1. What is bio-monitoring and give another example besides milkweed that
serves the same purpose?
_____________________________________________________________
_____________________________________________________________
2. What level of injury did you find?
_____________________________________________________________
_____________________________________________________________
3. If you found no ozone injury, what might this mean? How can you verify
your results?
_____________________________________________________________
_____________________________________________________________
3. What is a bio-indicator? How can using milkweed and other plants as bioindicators help us keep the air clean?
_____________________________________________________________
_____________________________________________________________
4. What are the advantages or disadvantages to using bio-monitoring
projects?
_____________________________________________________________
_____________________________________________________________
5. Compare your results with a local air-quality monitoring agency. Are they
similar? Different? What might cause the results to be different?
_____________________________________________________________
_____________________________________________________________
Name: _______________________
Earth Science
Date: ___________
Block: ___________
Conclusion:
Did the results of the experiment confirm or reject your hypothesis? Explain.
_____________________________________________________________
_____________________________________________________________
_____________________________________________________________
_____________________________________________________________
Links
1. Slide show of ozone and other damage to milkweed leaves:
http://dnr.wi.gov/org/caer/ce/eek/earth/field/milkweed/slideshowinde
x.htm
2. Bio-monitoring:
http://dnr.wi.gov/org/caer/ce/eek/earth/field/biomon.htm
3. Common milkweed:
http://dnr.wi.gov/org/caer/ce/eek/veg/plants/milkweed.htm