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Activity 4: Not Till It's Right
Grades: K-8
Associated Lesson Topics:
- Factors controlling germination
- Germination process
National Standards:
- SCIENCE:
Standard A, Standard C (K-4)
- MATH: Measurement
Standard, Data Analysis and Probability Standard
Planting the Seed...
Do you think that all seeds germinate as soon as they hit the ground?
If not, how do they "decide" when to germinate? If they come with a baby
plant and food inside, why don't they begin to grow right
away?
Teacher Information:
Wildflowers are flowering plants that grow in their natural state with
little interference from humans. In this activity, students will collect
wildflower seeds and germinate them back at school. Plan to collect wildflower
seeds when they are ready to be dispersed-when the fruit color changes
from green to dark brown or black. For most seeds, this occurs approximately
four to six weeks after flowering. Research beforehand which plants in
your region will be at this stage during the school year. And make certain
that the plants you are considering are not endangered.
Necessary Materials:
- The following are a few wildflowers that are relatively easy to start
from seed indoors and to transplant outdoors in the spring. The region
of the country in which you live will largely determine which of these
plants you are likely to find.
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Common name
Tickseed
Black-eyed Susan
Indian blanket
Columbine
Purple coneflower
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Latin name
Coreopsis lanceolata, Co reopsis
tinctoria
Rudbeckia hirta
Gaillardia pulchella
Aquilegia canadensis
Echinacea purpurea
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- Small paper bags
- Envelopes.
- Magic marker.
- Nail file.
- Petri dishes.
- Paper towels.
- Planting materials.
Procedure:
- Students should begin by collecting wildflower seeds. By inverting
the flower head in a paper bag and gently shaking it, they will release
the seeds.
- Have students transfer the seeds to an envelope and label it with
the name of the plant and when/where the seeds were collected. If possible,
students should collect seeds from several different kinds of plants.
This will enable them to observe differences among seeds.
- Dry the seeds. Place the seeds in open petri dishes or other small
trays and leave them in an area with good circulation for a few weeks.
Make sure to keep the different seeds separated and labeled.
- After the seeds are dry, the experimentation begins! Have students
try several different methods and combinations of methods to get the
seeds to germinate. Try each method with a "batch" of each seed type.
Each batch should have the same number of seeds. Below are some suggestions
for how to treat the seeds, but students should be encouraged to come
up with their own.
- Doing nothing.
- Soaking overnight. As an extension, students can weigh their batch
of seeds before and after soaking to determine the increase in seed
mass due to the imbibition of water.
- Scarification: Rough up the seed coat with a nail file, making
sure to not injure the embryo.
- Stratification: Layer seeds in moist paper towels and place them
in the refrigerator for a week.
- Scarification and stratification.
- There are two ways to continue the germination process. The first
is to fold a paper towel (creating more than one layer) to fit into
a petri dish. Moisten the paper towel thoroughly and then place the
seeds on the paper towel. Provide with plenty of sunlight and keep the
paper towel moist. Students can make observations of the seeds daily
and record (through drawings in their journal) what is taking place.
If this is the approach that you use, allow the students to observe
the process first and make suggestions about what is happening before
you teach them the stages of germination. Once the seeds are germinated,
they can be planted in pots or in the garden and grown for use in other
lessons.
Or...
- Students can plant the seeds directly into pots, moisten the soil,
cover the pots with clear plastic, and place them on a windowsill. With
this approach, students will not be able to observe the different germination
stages.
Harvesting the Crop...
With either approach, students can determine the success of the different
methods by noting how many seeds in each batch germinate. Younger students
can simply count the number of seeds that germinated in a given number
of days and record that number. Older students can record data in a germination
table (sample table provided below) and calculate the percentage of seeds
that germinated (% germination). Students can also create graphical representations
of their data. Based on these results, they can draw conclusions about
which method is most effective for each seed type. This is why it is so
important to keep the seeds labeled!
SAMPLE GERMINATION TABLE
| Seed type |
Date germinated |
# germinated |
% germination |
Sources
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