Curriculum / For Teachers / Grow

Structure and Function of Plants

Students learn that plants’ structures serve functions and observe capillary action by placing celery stalks in different colors of dyed water.

Structure and Function of Plants
Purple sage (Salvia leucophylla) / Photo credit: Anna Laurent

· This is a great activity to practice journaling and observation skills.

· Allow the students time to observe and record the absorption process.

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Capillary action is the process by which liquid nutrients and water move through narrow spaces in a plant’s stem (xylem and phloem) against the flow of gravity. This lesson illustrates how plants feed themselves.

Learning the structure of plants helps students understand how the function of one part leads to the health and stability of the whole organism.



· To learn about the structure of a plant

· To learn the functions of stems



LS1.A: Structure and Function

All organisms have external parts that they use to perform daily functions.

LS1.C: Organization for Matter and Energy Flow in Organisms

All animals need food in order to live and grow. They obtain their food from plants or from other animals. Plants need water and light to live and grow.



· Tall, clear glass or jar

· Masking tape and pencil

· Water

· Food coloring (red and blue work best)

· Scissors

· Celery stalk with bottoms freshly trimmed and leaves intact



· A few days in advance, make a sample celery stalk according to instructions to demonstrate how the process continues over time and reaches the leaves of the stalk.



Bring in examples of cuttings from other kinds of plant stalks to pass around (ex: parsley, basil etc).



1. Begin with a discussion of human body parts and what each does: what do our bones do? What does our mouth do? Explain that plants’ bodies have structures just like the human body. Each part of a grown plant has a function: » The roots absorb water and nutrients » The stem transports nutrients to all parts of the plant » The leaves make food from the combination of air, sunlight, and water and allow the plant to breathe.

2. Pass around the samples of other stems and/or have the students find different stem examples in the garden.

3. Bring the class back together. Fill a tall, clear glass or jar half full with water.

4. Explain that they are going to learn how celery’s stalk (stem) helps it live.

5. Add a few drops of food coloring to the glass and mix well.

6. Place the celery stalk in the glass or jar overnight. Mark the water level with a piece of masking tape.

7. The next morning, observe what has happened. Ask: Where has the water has gone? What has happened to the celery? Explain that water has been absorbed into the celery stalk, bringing the food coloring with it, changing its color. This shows how the plant gets water from its roots all the way to its leaves.



1. How do stems help plants?

2. Why were the leaves of the celery a different color?



· Take a second stalk with leaves and trim the bottom, cutting a slit up the middle and stopping an inch below the leaves. Add a different food coloring in each of two glasses and place one “leg” of the stalk in each.

· In a few days, observe what has happened. Each half of the celery stalk will have absorbed the colored water and the two colors will have blended together at the top of the stalk.