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

Grades: K-4

Associated Lesson Topics:

• Transpiration

National Standards:

• SCIENCE: Standard A, Standard C
• MATH: Measurement Standard, Data Analysis and Probability Standard

Planting the Seed...

Ask students to remove a leaf from the top of a plant. Have them break the leaf open and observe its contents. What do you notice? Where do you think the moisture comes from? How might it find its way to the leaf?

Teacher Information:

You can use this simple demonstration at the beginning of a lesson on transpiration. The following analogy may be useful for teaching about the cohesion-tension theory. If you suck on a straw that is in a glass of water, the water comes up through the straw into your mouth. The same thing is happening in the plant. With the straw, negative pressure is being created by your sucking. In the plant, negative pressure is being created by water evaporating off the surface of the leaf. The students can imagine the xylem, where water is conducted, to be a miniature straw inside the plant.

A fun way to conduct this experiment is to provide each student with a white carnation. You can coordinate this activity with a special holiday and have the class create appropriately colored flowers. For example, green carnations for St. Patrick's Day, pink carnations for Valentine's Day, or red carnations for Mother's Day. Students can then take their flowers home to enjoy!

Necessary Materials:

• Four single stems of Queen Anne's lace or white carnations.
• Food coloring (four colors).
• Four vases or glass beakers.

Procedure:

• Gather four single stems (with flowers) of either Queen Anne's lace or white carnations.
• In clear vases or glass beakers, mix water with food coloring to produce four different colors (for example, red, blue, green, and yellow).
• Cut the base of each stem on an angle (this increases the surface area over which water can be absorbed into the plant). Place each stem in a different color.
• Place the setup in a warm spot for 1 hour.

Harvesting the Crop...

What happens? How does the colored water make its way up to the flower? How might a plant's ability to move water up help it survive? Students can measure the rate at which the colored water travels to the flower. What factors might affect this rate? Do you think the amount of food coloring matters? What about the temperature? Now you can begin a lesson on transpiration.

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