Description: What happens to seeds that are exposed to very high levels of radiation? Will they grow normally?
Disciplinary Core Ideas (DCI, NGSS)
5-PS1-3, 5-ESS3-1, 3-5 ETS1-1, MS-ETS1-2, MS-ETS1-3, HS-PS4-4, HS-ESS2-3
Time for Teacher Preparation
To gather materials and set-up
1-2 Weeks Minimum. Passive observations as beans grow.
- Pen, Marker, or Pencil
- Student Data Collection Sheets
- Mung bean seed
- Irradiated Mung bean seeds (50,000; 100,000; 150,000 rad exposure)
- Potting soil
- Pots (2″ to 3″ pots)
- Small metric rulers
- Students should not put bean seeds, soil, pots, or metric rulers in their mouths due to choking hazard.
- Students should not try eating bean seeds or irradiated bean seeds.
Science and Engineering Practices (NGSS)
- Ask questions and define problems
- Plan and carry out investigation
- Analyze and interpret data
- Use mathematics and computational thinking
- Construct explanations
- Argue from Evidence
- Obtain, evaluate and communicate information
Cross Cutting Concepts
- Cause and Effect
- Scale, Proportion, and Quantity
- Energy and Matter: Flows, Cycles, and Conservation
- Structure and Function
- Stability and Change of Systems
The students develop a procedure to study the effects of radiation on mung bean seeds and other irradiated seeds. Students will observe and record data on the germination and development of the plants. Student data, results, and conclusions will be presented, supported, and defended by the students to the class.
- To define the terms radiation and irradiation
- To determine how irradiation affects the growth of bean seeds
- To determine how much radiation dose comes from nature and how much comes from the uses of radiation in society.
- To compare data
Irradiation is becoming increasingly more popular in the treatment of foods to kill bacteria, diseases and pests. A fear of radiation causes some people to believe that food that is irradiated becomes radioactive. The irradiated bean seeds in this experiment have been exposed to various levels of gamma radiation, but are not radioactive and are completely safe to handle.
You cannot tell how much radiation the seeds were given by looking at them. These seeds were harvested and irradiated after the plants were mature. However, you will be able to observe differences in the plants growing from these seeds. Each seed contains an embryo plant. When the gamma radiation passed through these seeds, it damaged some of the cells in the embryo. The greater the radiation, the more cells were damaged. Therefore, the resulting plants grown from seeds with greater exposures will show more abnormalities than those with lower exposures.
Teacher Lesson Plan:
Split students into groups of four and give each group four sets of bean seeds (control; 50,000; 100,000; 150,000 rad). Have each group plant their seeds in separate pots and set up a table to chart and graph the growth of the seeds over the next couple of weeks. Students should record height and observations of their beans at least twice a week. Remind students to water their beans as frequently as needed in order to take care of their plants.
It might be helpful to stress that the beans have been irradiated, but are not radioactive.
Students may also grow the seeds in test tubes of water and plant them once they have germinated.
NGSS Guided Inquiry
Have students design an experiment to discover about how much radiation each of their seeds was exposed to.
- Plant seeds into separate pots and water until the soil is moist. Alternatively, grow the seeds submerged in water inside of test tubes until they germinate and then pot them.
- Set up a data table to record height and observations of the bean seedlings. Observations should be made at least twice per week.
- Take care of your plants by watering them as frequently as needed.
- Graph data from your data table and deduce which seeds received which dose of radiation (control; 50,000; 100,000; 150,000 rad)
- Add a step to include listing the variables which must be controlled in this experiment.
- Examples of this include:
- exposure to sun or artificial light
- temperature of the surroundings
- whether seed is grown in soil or in water
- the amount of water added to the soil (students should measure the added water in milliliters).
Post Discussion/Effective Teaching Strategies
Questions provided on the Student Data Collection Sheets
- What happened? Why do you think the things you observed occurred? Were your observations and conclusions different from other students? Why? Who’s “right?”
- 100,000 rads or 150,000 rads is enough to kill a human. Did it kill all the plants? What do you think are some possible explanations?
- Test the student’s observations against the actual irradiated exposure of each plant.
- Have students make slides of each of the beans for viewing under a microscope.
- Try getting a couple more generations from the plants to observe successive generations.
- If radiation increases on earth, what effects do you think it will that have on plant growth? On other organisms? On humans?
- What do you think happened to the cells of the irradiated Mung bean plants?
- Why do we use irradiation to prevent food from spoiling?
Los Alamos National Laboratory (1992). Detecting the Invisible: The SWOOPE Radiation and Radon Discovery Unit