Plants and Weather

INTRODUCTION

Plants take up water through their roots. This water is typically filled with nutrients that the plant needs. Plants use some of the water to produce food. The water continues to rise in the plant by capillary action to the leaves. Excess water that the plant does not need is released by the plant through a stoma (which is a port at the bottom of a leaf that opens to allow evaporation of water. The average birch tree transpires about 80 gallons of water each day into the atmosphere.¹ This experiment will show the uptake of water by a plant and will also allow the measurement of transpiration (the release of water to the air by plants).

MATERIALS

• Celery or white flower
• Potted plant
• Clear plastic bag
• String or large rubber band
• Glass
• Food coloring

WHAT TO DO

1. Cut the bottom section of a piece of celery. Place the piece of celery (or the flower) in a glass of water that is colored with food coloring. Check the celery or flower twice each day.
2. Count the number of leaves on the potted plant. Water the potted plant with a water dish below the plant. Wrap the clear plastic bag around the plant. Make sure the bag is tightly sealed around the plant.
3. Make a "control bag." Use the same size bag, and inflate by holding it open in the air. Close off the bag with the same type of tie as used for the plant.
4. Place the plant and the control bag in a warm location. Leave the bags to sit there for a couple of days. Observe them closely each day.

QUESTIONS

1. After two days, what is different about the contents of the two bags?
2. Measure the amount of water collected from the bag that was wrapped around the plant. Divide that volume of water by the number of leaves. This will tell you how much water each leaf is releasing to the atmosphere in two days time.

EXTENSION

1. Compare how much water is collected from the plant during after daytime conditions or after nighttime conditions. Is the amount different?

SOURCE

"How Weather Works," Michael Allaby, Reader’s Digest, Dorling Kindersley Limited, 1995, p. 44.
"Science Is . . . A Resource Book for Fascinating Facts, Projects, and Activities." S. Bosak, Scholastic Canada, 1998, p.278.

Grade Level: This experiment is expected to be appropriate for grades K and above.

© S. Olesik, WOW Project, Ohio State University, 2002.