From Seed to Seed:
Plant Science for K-8 Educators

Activity 10: Root Routes

Grades: K-4

Associated Lesson Topics:

• Response to gravity
• Comparison between taproots and fibrous roots
• Umbelliferae (carrot) family
• Roots as food

National Standards:

• SCIENCE: Standard A, Standard C, Standard F

Planting the Seed...

Do you think all roots look the same? If not, how do plant roots differ? One way to answer this question is to investigate the root systems of the weeds that you pull out of your schoolyard garden plot. Do roots always grow down? How do roots know which direction to grow? Can you think of a way to make roots grow upward?

Teacher Information:

Part I. In this activity, students will grow plants with fibrous root systems and plants with taproots. Plants with different root systems differ in the way they capture water resources. The shallow roots of the fibrous root system force these plants to capture water and nutrients from near the surface of the soil. Taproots, on the other hand, are able to extract these resources at greater depths. As a result, plants with taproots are not as likely to be affected by short-term shortages in water supply.

Part II. Since you are already talking about roots, you might also investigate the phenomenon of geotropism. Planting bulbs is a great way to demonstrate gravitropism. Students can experiment with planting bulbs in the soil facing different directions, to explore whether roots will always grow down and the shoots will always grow up.

Necessary Materials:

• Seeds of plants with taproots: carrot, beet, radish, dandelion, Queen Anne's lace.
• Seeds of plants with fibrous root systems: pea, corn, bean.
• For classroom gardeners, transparent planter (e.g., root view box).
• Bulbs.
• Planting materials.

Procedure:

• Part I. Students plant the seeds. If they are going to grow these plants in the classroom, students should plant the seeds in a transparent planter so they can view the root systems. If the plants will be grown in the garden, students can view the root systems at the end of the growing season when the plants are harvested.
• Part II. Students come up with their own suggestions about to get roots to grow up. For instance, they might plant some bulbs right side up and some upside down and document what happens. What did you notice about the bulbs that you planted? Did all of the bulbs grow? What can you infer about the direction of root growth? How do you think this helps the plant? Did it take some bulbs longer to produce shoots? If so, what do you think caused this to happen?

Harvesting the Crop...

How might different types of root systems benefit plants? Many gardeners know that it is better to water their gardens thoroughly once or twice a week rather than a little bit every day. Watering a garden a little bit every day enables the roots to grow in the upper layers of the soil where water is plentiful. For a plant, life near the surface can be treacherous, especially during a drought or when the gardener forgets to water for a few days! Investigate this phenomenon with your students by planting several plants (with both types of root systems) in their own containers or in separate sections of the garden. Using the same amount of water for both, water half of the plants thoroughly once a week and water the other half daily with just enough water to moisten the surface of the soil. Make sure that the plants are otherwise treated identically. After exposing these plants to this treatment for several weeks, simulate a drought and see which plants tolerate it better. What do you see? Why do you think this happened? What can you conclude about the best way to water a garden?

Sources

•Bulbs
Flowerbulb www.flowerbulb.co.uk
Holland Flower Bulb Company www.hfc-flowerbulbs.nl
Florajacs www.florajacs.co.uk

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