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Plants have vascular structures - like the veins in animals' bodies; tubes that carry liquid, called xylem and phloem. Xylem transports water and nutrients upwards from the roots to the stems and leaves. Phloem transports food produced by photosynthesis within the leaves mostly downward to the rest of the plant. Xylem and phloem make up an extensive transportation system in vascular plants!

Celery rainbow

By: Sam Lucas

Have you ever wondered how plants transport water? In this activity you will have the chance
to watch it happen before your eyes!

Materials:

  • Celery Stalks (green onions, lettuce, or white flowers will also work)

  • Food Coloring

  • Water

  • Cups/glasses/jars (anything that holds water)

  • Knife

Procedure

  1. Fill cups with at least 1/4 cup of water.

  2. Add drops of food coloring to the cups (the more food coloring you add, the faster you will see results!) I used blue, red, and yellow food coloring.

  3. Cut off the bottoms of the stalks for a fresh cut.

  4. Place celery stalks into cups.

  5. Let sit and observe progress throughout the week.

  6. Record observations at least once a day.

coolimagecelery.jpg

Why?

Xylem vessels are long, thin tubes that span the length of the plant. Water moves up the xylem through a process known as capillary action. Capillary action occurs when the properties of cohesion and adhesion unite and overcome the downward force of gravity. A common example of capillary action can be seen when a straw is placed in water and the water appears to move up the straw.

Capillary action is really interesting, and is important for living things. If you would like to learn more, check out this cool site by the U.S. Geological Survey.

Cohesion and adhesion are properties of water. Cohesion occurs when identical molecules are attracted to each other; in this case, water molecules are attracted to other water molecules causing them to stick together. Adhesion occurs when a molecule is attracted to a different type of molecule, causing the water molecules to stick to the walls of the xylem.
Cohesion makes the water in the xylem act as one large molecule of water, and adhesion forces this water to climb upward through the plant’s thin tubes. These properties allow water to be transported, against the forces of gravity, for hundreds of feet in giant trees, from the roots to the top of the tree.

In our experiment, the water gradually moved up the celery, changing the color of the stalk and leaves over the course of five days.

additional cool resources

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Science & Plants for Schools

Click to see a great visual of the movement of water and sugar through plants.

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