Carry out a range of experiments

Key Questions
* What do plant seeds need to germinate?
* What changes do seeds and seedlings undergo during germination and early growth?

Time Frame:
On-going for one week or more.

For each group of 2 - 5 students:

* Stapler and staples
* Water
* Wheat seeds
* 1 sealable sandwich bag
* 1 paper towel (any type will work)
* String or thread
* "Planting Seeds in a Baggy" worksheet
* Worksheet: "Student Log Sheet"

Getting Ready
Before teaching your class, assemble all of the materials. Photocopy the "Planting Seeds in a Baggy" worksheet for each group of students. You may want to try the activity first to make sure classroom conditions allow rapid germination of the seeds. Roots should appear within one or two days after the seeds have been soaked in water. NOTE: Since the seeds will germinate quickly, you should begin this experiment at the beginning of the school week. Secure a location to hang the plastic sandwich bags. Sunlight is not necessary for seeds to germinate. HINT: Binder clips and push pins may be used to hang the plastic bags on a board.

Seed Germination Student Log Sheet
Click here to get the printable version of the log sheet

Classroom Activity

1. Introduce the concept of the plant life cycle by comparing it to the human life cycle of birth, growth and reproduction. Point out similarities and differences with the corresponding plant life cycle stages: seed germination, plant growth and seed production.

2. Ask students "What conditions do you think seeds need to germinate?" (moisture, soil, light, and temperature may all be factors with moisture being essential).

For older students, challenge them to think about the roots "attraction" toward the source of a gravitational pull (the Earth!). This effect is called "gravitropism."

3. Explain that students will germinate wheat seeds using the "baggy method."

4. Demonstrate the baggy method of germination (see "Planting Seeds in a Baggy" worksheet).

5. Hand out a "Planting Seeds in a Baggy" worksheet and seed germination supplies to each group of students. Have them assemble the germination experiment following the steps on the worksheet.

NOTE: Classroom light will work for the germination.

6. If you would like your students to do controlled experiments, they can work in teams to try the following:

a) To test the effect of water on germination, put different measured amounts of water in different baggies.

b) To test the effect of light as a variable, place baggies in various locations in the classroom that offer varying light levels. For example, place baggies inside a desk or in a shoe box with 'windows' of a few sizes cut into the sides to allow some light to enter.

c) For older students, challenge them to design experiments to test other variables, such as temperature or gravitropism. To investigate gravitropism, have some students try turning their baggies. Depending on the rate of growth, they may observe results in the growing roots/shoots overnight or in a couple of days. They may continue to turn the baggies if they wish; see what happens.

Be sure that your students test only one variable at a time. For example, when testing the effect of light, keep all those baggies at about the same temperature. When testing temperature or moisture, keep all the bags in the same light conditions. For older students, each experiment group may be given responsibility for testing a particular variable. For younger students, it may be best to keep it simple and have the whole class test one variable or just stick to observing the germination process and do no other experiment.

7. Have students monitor the germination and development of their seedlings over one week's time or longer. Every day, they should look for changes in the seeds and seedlings and note them in their lab notebooks or on a log sheet (sample at the end of this activity). Students should record the daily changes in the length of roots, the colour and shape of the individual seedling parts (these could be represented by drawings), the temperature in the classroom, how much light the seedlings receive, and how many of the seeds successfully germinated each day.

Wrap-up Session
1. Discuss the process of seed germination and allow students to share their findings about the conditions that led to successful germination and early plant growth. Ask the students questions such as:

What conditions are necessary for seeds to sprout?

What are the changes that the seed and seedling undergo after germination?

Ask selected students to draw each of the stages on the board and identify parts of the seedling: the root, shoot and leaves.

Why do plants need the inactive, dormant seed stage? (To allow the seeds to "wait out" harsh winters and other times when a newly sprouted plant would not survive.)

2. If the class did specific experiments, have the experiment teams present their results and conclusions to the whole class in a "scientific convention."

3. Have the students break open seeds and look for the parts of the seeds. (Seeds are protected by a hard shell, known as the "seed coat," that keeps the seed from germinating until moisture, light, soil and temperature levels are favorable for plant growth. Inside the seed coat is the immature plant, known as the "embryo," and enough nutrients to support the seedling for a short amount of time after it sprouts.) Ask the students if they can recall what happened to the seed coat when it got wet? (It swelled and softened, allowing a root to emerge.)

4. For older students, you may want to explain that the first set of leaves is called the primary leaves. After the second set of leaves appears, the plant can usually begin manufacturing its own food in the process known as photosynthesis, which uses sunlight for energy. After the plant matures, it will produce new seeds for the next generation of plants.

5. Students can compare their seed "success rate" with that of the NASA scientists. Plant experiments in space took place during a joint mission of the Russian spacecraft Mir and the U.S. space shuttle in 1995, using wheat seeds. Although there were some problems with the lighting and watering equipment, almost half of the seeds sprouted in space-a germination rate of 50%. Ask students why they think the germination rates in the classroom may be different from those of seeds grown in space (different kind of plant, differences in light: sunlight vs. artificial light, microgravity effects, equipment problems).

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