PREINSTRUCTIONAL

• Students will be introduced to ways in which the plants in the desert obtain water.
• Students will identify the importance of a desert plant's roots.

• Eyewitness Science book on Deserts.
• One shallow container for each group.
• Sand, enough to fill each container two to three inches.
• Water
• One spoon for each group.

DURING INSTRUCTION

1. Review the hot desert conditions, and brainstorm ways in which desert plants could obtain water. Ask the students to take out their journals.
2. Give each group a pan with sand in it.
3. Have each group pour one-fourth to one-half cup water evenly over the surface of the sand. Ask students to predict where the water will settle as it soaks in.
4. Ask the students where the most water in the pan is, and to find that place.
5. Ask the students how plants could get the water that is present deeper in the ground.
6. Discuss the importance of roots in desert plants.
7. Show the students page 19 in Eyewitness Desert, showing the roots of a cactus, and the cross-section of a cactus.
8. Ask the students to think of other ways a desert plant might obtain water. (long roots, spread roots to collect water when it rains, absorb dew through leaves) How might they keep this water? (reducing leaf size and losing leaves in time of drought, storing in stem as barrel cactus does are possible answers).
9. Ask the students to respond to the lesson in their journals.

POSTINSTRUCTIONAL

• Were the students able to predict ways in which a desert plant obtains water prior to the experiment?
• Could the students find the area with the most water in the sand?
• Did the students identify the importance of roots in desert plants?
• Were the students able to identify any other ways in which a cactus might use its roots to get water? Keep water?
• Did the journals show the relation between long roots and the ability to obtain water that is deep in the sand?

• Take the students out to a sandbox on the playground or nearby park. Dig a small hole in the sand, and notice the moisture that is not present on the surface. Feel the sand, and notice the cooler temperature. Ask the students what roots would be better to have in the desert - long or short.
• Ask the students what the quickest way to gather water would be during a rare rainfall - would it be better to take the water right away, or wait until it soaks into the sand? What roots would be best to have during a rainfall?
• If a student does not understand, repeat the experiment during study hall with the picture of the cactus roots in front of the student. Allow him or her to make the relation between deep water and long roots.