Spongy: How Does Water Move Through Moss?
How does water move through moss?
- 1 tablespoon (15 ml) tap water
- Sheet of typing paper
- Paper towel
- 2-inch (5-cm) section of dry sphagnum moss (available at a plant nursery or florist) magnifying lens timer
- NOTE: The section of moss should look like a tiny leafy stem with roots.
- Fill the spoon about one-fourth full with water.
- Carefully set the spoon on the typing paper. Use the paper towel to blot up any water that spills onto the typing paper.
- Place one end of the moss in the water in the spoon. Allow the other end to touch or hang above the paper.
- Use the magnifying lens to observe the moss as often as possible for 30 minutes. NOTE: Keep the wet moss for the next experiment.
The moss slowly becomes wet, beginning with the end in the water. Finally, water drips off the other end onto the paper.
As water moves through moss, it is distributed throughout the plant by a process called diffusion. Diffusion is the spreading out of a material from a concentrated (to be crowded with a material) area to a less concentrated area. The dry moss in this experiment acts like a sponge. It absorbs water from the spoon. The water moves from cell to cell as it diffuses throughout the plant.
Moss absorbs water this way because it is a nonvascular plant. There are two basic types of plants: vascular plants and nonvascular plants. Vascular plants have a vascular system that contains bundles of tubes called vascular tubes, which transport sap (a liquid containing water and minerals or food) throughout the plant (See chapter 3, "Climbers," for more information about vascular plants.) Nonvascular plants, such as moss, do not contain a vascular system. Water, minerals, and food are transported through nonvascular plants by diffusion.
Will water continue to move through wet moss? Repeat the experiment, using the wet moss from the original experiment Add 1 drop of green food coloring to the water in the spoon. Note the color of the water moving through the moss and that of the water dripping onto the paper. Science Fair Hint: Take photos or make drawings of the moss every 5 to 10 minutes. Use them as part of a project display to represent the results of the experiment.
- To live, a plant on land must obtain and retain water, but it loses water through its outer surface. However, the outside of mosses and most plants is covered by a waxy film called the cuticle. The cuticle keeps a plant from losing too much water because it slows down the passage of water vapor (water in the gas state) through the plant's outer surface. Demonstrate the effect of the cuticle on water loss by dampening 2 paper towels with tap water. The towels should be wet but not dripping. Roll up one of the paper towels and lay it on a cookie sheet. Roll up the second paper towel in the same way, but wrap it with a piece of waxed paper about the size of the paper towel roll so that the outer surface of the towel is covered by the waxed paper. The waxed paper represents the cuticle covering a moss's epidermis. Secure the top and bottom of the waxed paper-covered towel with large paper clips, and place the covered towel on the cookie sheet. Set the cookie sheet where it will receive direct sunlight. Unroll the towels after 12 hours and feel each.
- Mosses grow best in shady areas and generally grow on the ground near and on the north side of trees. See for yourself that the north side of a tree has more shade. Find a tree that is not growing near other trees and buildings. Use a compass to determine the directions north, south, east, and west. Mark these directions by writing N, S, E, and W on separate index cards. Use tape to attach each card to a pencil, and insert each pencil in the ground around the tree in the appropriate place. Observe the tree as often as possible on a sunny day. Take photos or make sketches of the tree and its shadow during each observation.
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