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Class Activities |
Chapter 38: Translocation And Water Relations Of Plants |
1. Relevance of Topic
This chapter holds the same relevance as the preceding one, in presenting various interesting adaptations of plants for living in a large variety of conditions.
Any student with a specialized interest in plants should find this material to be useful in rounding out the functions of various plant tissues and cells, and also in explaining the adaptive significance of various structures and "behaviors."
2. Continuity
This chapter follows from the preceding one in analyzing the structures and functions of specialized plant tissues and cells.
The next chapter continues the analysis of plant characteristics.
Throughout the coverage of this material, a continuing emphasis on the adaptive significance of plant features will help students connect and integrate the material from one chapter to the next.
3. Demonstration Activities
Text section 38.1
1. Show Figure 38.1 and discuss the function of the stomata.
2. Show Figure 38.2 and discuss where stomata are typically located in various types of plants.
3. Discuss the role of guard cells, and show Figure 38.3.
4. If possible, show a video of the guard cells at work.
Text section 38.2
1. Show a micrograph of a root cross section and point out the xylem when discussing its role in water transport.
2. Discuss root pressures and the fact that these do not occur in conifers. Ask the class to explain how conifers take up water.
Text section 38.3
1. Discuss the three forces that move water upward in plants: capillarity (Figure 38.5), cohesion, and a pull on the xylem fluid from above.
2. Show Figure 38.8 and emphasize the amounts of water lost through transpiration.
3. Discuss or perform a basic transpiration experiment where the plant is weighed before and after transpiring.
4. Ask the class to provide ideas about adaptations by which plants control water loss (e.g. rolling up their leaves in the heat of the day).
Text section 38.4
1. Discuss translocation as the basic function of phloem.
Text section 38.5
1. Define nastic movements and show pictures or time lapse videos to illustrate this, including Figures 38.11—38.13.
2. Define tropic movements and again show pictures or videos to illustrate it.
Text section 38.6
1. Open this text section by discussing and asking for ideas on the adaptations necessary for plants to balance photosynthesis, transpiration, and translocation.
2. Show photos of plants that are challenged in each of these three functions.
3. Give general information on how plants can cope with these challenges (e.g. changing the rates of each of the three functions).
Text section 38.7
1. Introduce this section with photos of plants that are challenged by extreme temperatures.
2. Discuss the differences among the processes of radiation, convection, or transpiration, and use commonly understood examples (e.g. a fire radiates heat) to make sure students understand all three processes.
3. Discuss how heat is lost from a plant.
Text section 38.8
1. Generally distinguish sun plants from shade plants.
2. Show photos of each type of plant.
3. Again involve the students in a discussion of the challenges plants must overcome if they are in either category, shade or sun, and ask students to provide ideas on adaptations that have evolved to cope with these challenges.
Text section 38.9
1. Show Figure 38.20 and discuss xeromorphic characteristics.
2. Bring living specimens of xerophytes to class when discussing their special adaptations.
Text section 38.10
1. Make connections to xerophytes when discussing halophytes and their similar characters.
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