Colorful Celery

Grade Level: 6th; Type: Botany

Objective:

The goal of this project is to simulate the capillary function within plant structure. The experiment procedure includes intervals for examining the results and tracking the journey of the moisture over time. Variations to the experiment offer added dimensions.

Research Questions:

How do plants retrieve water from their surroundings? How does the water travel throughout the plant?

Plants draw water from their roots through hollow capillaries that act like straws. Over an extended period of time, the water travels from the roots through the plant’s system. This process is called osmosis and relies on the increasing narrowing of the capillaries as they extend up the stem.

The independent variable in this experiment is the food coloring. The dependent variable is the color of the celery. The constants are the water and the glasses. See the procedural note for additional independent variables that can be tested.

Materials:

• One full bunch of celery.
• Food coloring.
• 7 Glasses—the same size.
• One sharp kitchen knife.
• One vegetable peeler.
• Logbook. 

Experimental Procedure:

1. Fill the eight glasses with water about an inch from the rim.
2. Add red food coloring to four of the glasses. Be sure to use the same number of drops in each glass.
3. Add blue food coloring to four of the glasses. Again be sure to use the same amount in each glass.
4. Slice six stalks of celery from the bunch, making sure that the cut is straight across. Likewise, slice the leafy tops off six of the celery stalks, leaving the seventh alone.
5. Place three of the stalks in the glasses with red water and three in the glasses with blue water.
6. Slice a seventh stalk from the bunch, but leave the leaves on top. Slice this stalk vertically, stopping below the leaf region.
7. Gently put one “leg” of the seventh stalk in the remaining glass of red water and the other “leg” in the remaining glass of blue water.
8. After 2 hours, lift the stalks and observe the bottoms versus the tops. (Don’t remove the seventh; that one will remain untouched until the end of the experiement.) 
9. Record your observations and return the stalks to their glasses. Make sure that the bottom of the stalk enters the glass first.
10. Remove one stalk for closer inspection. Slice through the stalk about 2 cm from the bottom and examine the cross section. Peel the celery from the bottom to examine the vertical layers.
11. Repeat at 4 hours, 8 hours, 12 hours and 48 hours. You have five intervals and six stalks—one extra in case of accidents.
12. After 48 hours, observe the seventh stalk carefully. What color are the leaves? Cut and peel as necessary to create significant notes. 

[NOTE: To add dimensions to the experiment, play around with temperature and light as independent variables to test if they affect the capillary action.]

Terms/Concepts: Capillary; Osmosis; Surface tension; Gravitational forces

References:

• Experiments with Plants, Salvatore Tocci (2002)
• http://science.jrank.org/pages/1182/Capillary-Action.html.
• Plant Parts, Richard and Louise Spilsbury (2008)
• What is a Plant, Bobbie Kalman (2006)