BioEd Online

Teacher Background

Almost all life on Earth depends on energy from the sun. Green plants and other organisms, such as algae (seaweeds) and some bacteria, are able to trap and store energy from the sun through a process called photosynthesis. The green color of plants and algae is caused by chlorophyll, a green pigment that is primarily responsible for the “light-trapping” part of the process. Sugar is the initial product of photosynthesis. In fact, more than 150 million tons of sugar are produced by the plants on Earth each year! Plants use some of this sugar to provide energy for life. They also use it as raw material to make starches, which are long molecules that can store energy until it is needed.

Plants need light energy, water, and carbon dioxide from air for photosynthesis. They need additional chemicals, called nutrients, to manufacture the many other molecules necessary for life. Nutrients must be dissolved in water before they can be absorbed. Aquatic plants and algae can take the nutrients they need from the water around them. Land plants absorb dissolved nutrients from water in soil through their roots. Three of the most important plant nutrients—nitrogen, potassium, and phosphorous—are common ingredients in most lawn fertilizers.

Plants cannot walk from place to place in search of resources. However, they are capable of some kinds of movement. For example, flowers open and close, stems bend toward light, and leaves and flowers follow the movement of the sun.

Plants and other photosynthetic organisms are called producers. Other organisms, such as animals and fungi (mushrooms, molds, and their relatives), rely on foods consisting of the sugars, starches, and other molecules “produced” by plants.

Objectives and Standards

Concepts

• Plants have basic needs.

• Plants need sunlight, water, air, and nutrients from soil.

• Plants can survive and grow only when all their needs are met.

Science Skills

• Observing

• Predicting

• Comparing

• Contrasting

• Recording data

• Interpreting data

• Generalizing

• Graphing

Mathematics Skills

• Observing

• Charting

• Identifying patterns

• Measuring

• Sequencing

• Graphing

Language Arts Skills

• Listening

• Communicating

• Identifying words

• Developing vocabulary

• Understanding word meanings

• Developing comprehension skills

• Writing

• Using descriptive language

• Following directions

Materials and Setup

Teacher Materials (see Setup)

• 20 cups of potting soil (approx. 3 lbs.)

• 4 resealable plastic bags, 12 in. x 15 in. (gallon-sized)

• 4 plastic plates, 10¼ in. diameter

• Fresh radish

• Package of radish seeds (approx. 500 seeds; see Setup)

• Paper towels

• Permanent marker

• Plastic knife

• Plastic teaspoon

Materials per Group of Students

• 4 peat pots, 3 in. (prepared)

• Clear plastic cup, 9 oz. (prepared)

• Fresh radish

• Plastic knife

• Plastic teaspoon

• Plastic tray

• Spray bottle (water mister)

Materials per Student

• Hand lens

• Paper towel

• Plastic teaspoon

• Copy of “My Own Radish Garden” and “My Science Journal” student sheets

Setup

1. Part 1 requires at least three weeks to complete. Part 2 requires one to two weeks to complete, depending on how quickly the radish seeds sprout. To save time, you may want to begin Part 2 shortly after setting up student mini-gardens in Part 1. 

2. For Part 1. Place materials for each group on trays in a central location. In advance, fill each peat pot two-thirds full of soil for students. Small disposable cups, with a hole punched through the bottom, can be substituted for peat pots (prepare as above). Also, place about 40 radish seeds in each of six cups (at least 6–10 seeds per student in each group).

3. For Part 2. Assemble supplies for the teacher-led activity: four small plastic plates, paper towels, plastic spoon, radish seeds, water mister, and four gallon-sized resealable plastic bags that are labeled “Garden 1,” “Garden 2,” “Garden 3,” and “Garden 4.” 

Procedure and Extensions

Part 1. Create individual radish gardens

1. Ask students, Are plants living or nonliving? How do we know? (Plants are living because they grow, have offspring, use resources, have a life cycle). Are seeds plants? Help students understand that seeds are living parts of plants and that seeds contain all the necessary materials to start a new plant under the right conditions. Ask, What do you think plants need to grow? Record responses on a classroom chart. For younger students, you may need to use drawings or pictures to indicate needs (sunlight, water, nutrients, air, space). 

2. Introduce the radish planting activity by discussing radishes with the students. Ask, What do you know about radishes? (plant, red, small, vegetable, etc.). Show the class a radish and give each group of students a radish and a few radish seeds. Have students cut their radishes apart. You may wish to cut radishes for younger students. Have them observe the radish and seeds with their hand lenses.

3. Distribute the student sheets. Explain that each student will plant his or her own radish seeds and watch them grow over the next few weeks. Using a spoon, demonstrate how to plant radish seeds just under the soil in a peat pot, and how to mist the soil lightly.

4. Label the pots with each student’s name. Give each student his or her own peat pot. 

5. Give each group of students a cup of radish seeds and a plastic spoon. Have each student plant about 6-10 seeds in his or her own pot.

6. Have students place their pots in a sunny place or under a grow light. Students should wash their hands when the planting is completed. 

7. Each day, ask students to observe their radishes. Have them record the radishes’ growth by writing or drawing on their “My Own Radish Garden” student sheets at least once per week. When the soil in the cup is dry to the touch, students should mist it lightly. You may also want students to measure the changes in plant height, using a paper clip chain or marked straws, every 2–3 days. They may also create graphs to record the growth of their plants.

8. After the radishes have developed (approximately 3–4 weeks), allow students to remove them from the pots. Have students wash the radishes thoroughly. They should use descriptive language to record their observations about their radishes. Point out to students that the edible portion of the radish plant actually is part of the root system. Older students may want to measure the circumference (distance around) or length of their radishes.  

Part 2. Investigating needs of plants

1. Ask students, What would happen to the radishes if one or more needs for plant growth were left out? (e.g., no water, no sunlight, or no soil). After students respond, mention that their suggestions will be applied to create four experimental radish gardens.

2. Explain to students that they will observe, over the next week or so, the progress of radish gardens that have four different sets of growing conditions. Begin assembling Garden 1 (control) and explain the steps you are taking as you assemble it.

   • Fold a paper towel in half and place it on a plastic plate.

   • Sprinkle 2 heaping teaspoons of potting soil across the top of the paper towel.

   • Sprinkle approximately 10–20 radish seeds onto the soil.

   • Lightly spray the soil surface with the water mister so that it is moist, but not soaking wet.

   • Carefully slide the plastic plate into a gallon-sized resealable plastic bag that is labeled “Garden 1.” Seal the bag.

   • Place Garden 1 in a sunny spot. 

3. Ask students, Does this radish garden provide everything that the seeds will need to grow? Make sure that students identify soil, water and sunlight as being present. Air also is present inside the bag.

4. Include students in the preparation of the other gardens, each of which will be missing one requirement for healthy seed germination (sunlight, water, or soil). See the "Garden Treatments" chart (sidebar) in the Living Things and Their NeedsTeacher's Guide.

   • Place Garden 2 (no sunlight) in a dark place.  

   • Place Garden 3 (no water) in a sunny spot or under a growlight.  

   • Place Garden 4 (no soil) in a sunny place or under a growlight. 

Part 3. Observing experimental gardents

1. Each day, have students check the gardens to make sure that the towel or soil is moist (Gardens 1, 2, and 4 only). Allow assigned students to mist the gardens with water when necessary. If bags become clouded with condensation, leave them partially open to allow the excess moisture to evaporate.
   
   Note. Bags that are allowed to stay too damp probably will develop a growth of mold. If mold appears, seal the bags and do not reopen.

2. Students should observe the gardens daily or every other day and record their observations on their science journal student sheets. The observations also can be recorded during the week on a class chart (see "Garden Observations" chart, PDF).  

3. At the end of one or two weeks, as a culminating activity, ask the class, What differences have you observed about the seeds (sprouts) in the experimental gardens? Prompt students to notice that the seeds with sunlight (Garden 1) developed green leaves and are growing normally; the seeds in the dark (Garden 2) germinated, but did not turn green or develop normally; the seeds without water (Garden 3) did not germinate; and that the seeds without soil (Garden 4) did not grow very much.

4. Guide students toward understanding that seeds need water to germinate, but that they also need nutrients (in soil) and sunlight to grow and develop. You may want to point out that air, also needed by plants, was present in all of the bags.

Extensions

• Make radish roses, dip, or a salad with radishes to share with the class.

• Bring other examples of vegetables to class for students to identify and examine.

Handouts and Downloads