Sub-Concept: Germination and Seedling Growth
Agricultural Context: The germination of various agricultural crop plants is very important
financially to producers; therefore, it is important for all phases of the germination process to
proceed efficiently.
Exercise: Examine Factors Affecting Seedling Growth: Oxygen Deficiencies
Applied Principle: After germination, seedling growth is a critical phase, requiring specific
conditions to exist. One of these is appropriate levels of oxygen.
Goals:
Preparation Time: 15 minutes 12 hours in advance; 30 minutes immediately prior.
Materials:
Materials for group experiments will vary. Each group should compile a list of needed materials
as a part of its experiment design.
References: Trudeau, M. (1994). "Plant Morphology and Taxonomy." Ithaca, NY: Cornell
Instructional Materials Service.
Osborne, E.W. (1994). Biological Science Applications in Agriculture. Danville, IL: Interstate Publishers, Inc.
2. Explain that seedling development is a critical phase in the life of a plant, requiring certain
environmental conditions.
3. Lead the students in a discussion of what factors might affect seedling development. Write
possibilities on the board (or have a student write them). Answers could include, but are not
limited to: temperature, type of seed, availability of water, salinity of water, and mechanical
damage.
As a part of e discussion, encourage the students to hypothesize about each factor, and why they
arrived at their answers.
4. Divide the class into 2-person groups.
5. Provide each group with 2 jars with airtight lids, 20 bean seeds that have been pre-soaked for
12 hours, paper towels, 1 steel wool pad, and water.
6. Lead the class in a review of the steps in the scientific process. Emphasize that these steps
must be included in their experiment designs.
7. Steps in the experiment:
a. Loosely stuff paper towels in both jars.
b. Place the steel wool pad in the center of 1 jar, as close to the bottom as is practical.
c. Place 10 pre-soaked seeds in around the sides of each jar, keeping them in contact with the paper towels.
d. Wet the contents of each jar, leaving approximately 2 to 3 cm. of water in the bottom of each
jar.
e. Observe the contents of each jar for 7 to 10 days.
f. Observe the steel wool after 10 days.
g. Record the observations.
8. Allow students to posit alternative hypotheses, to create alternative experiments, and test them.
Below are some ideas you may wish to offer to the students in designing their experiments:
Temperature Effects: May test seedling growth at room temperature, in a refrigerator, under a
lamp, etc. Can it be too cold or too hot for seedlings to develop? What does that mean about the
seed? Are there different temperature limits for different types of seeds?
Water Salinity Effects: Examine seedling development with various saline solutions. Treatments
could be: 30 ml distilled water, 30 ml tap water, 30 ml distilled water plus 1/4 teaspoon salt, 30
ml distilled water plus 1/2 teaspoon salt, 30 ml distilled water plus 1/2 tablespoon salt.
Seed Variation Effects: Do different types of seeds develop differently? What about different
varieties of the same seeds?
Seed Damage Effects: Mechanical damage to seeds during cleaning and packaging may have
some effect on imbibition, germination, and seedling development. What if the seeds have cracks
in their seed coats? (If there are no cracked seeds, mechanical damage may be simulated by
dropping them from about 5 feet onto a hard metal surface.)
9. Instruct groups to gather materials and set up their experiments. Be sure to carefully supervise
each group.
10. After all data has been gathered from the experiments, each group will present their findings
to the class.
Oral reports should include all steps in scientific process. Students should especially emphasize
the implications of their results.
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