Lesson 7.5 Xylem tissue

Learning Activity 1

Answer the following questions in your exercise book.

1. List three characteristics of xylem tissue.
2. List the two functions of xylem tissue.
3. List the four different types of cells that make up xylem tissue.
4. Study Figure 7.23 on p.142. In your own words, describe how xylem vessels are formed.

Learning Activity 2

Answer the following questions in your exercise book.

1. Explain the role of hydrostatic pressure in moving water up xylem vessels.
2. What prevents the walls of the xylem vessel from collapsing?
3. Explain what is meant by mass flow and what in the water molecules cause this.
4. What is the purpose of the pits?
5. Study Figure 7.24 which shows the distribution of tissues in the stem of a dicotyledonous plant. Copy the diagram into your notes. Take careful note of the arrangement of the vessels.

Learning Activity 3

Answer the following questions in your exercise book.

1. How can plants raise the water pressure at the base of the vessel?
2. Is water transport in plants an active or passive process? What is meant by that statement?
3. Answer Questions 7.8-7.9 (p.143).

Learning Activity 4

Answer the following questions in your exercise book.

1. Study Fig. 7.25 and 7.26 on p.144.
   1. What is different about the arrangement of xylem vessels in the root compared with the stem?
   2. Explain briefly how water moves from the soil through the root hair to the xylem
2. Describe the apoplastic pathway - Refer to Fig. 7.27a.
3. Describe the symplastic pathway - refer to Fig. 7.27b.
4. List the similarities and differences between the apoplastic and symplastic pathways.
5. Explain why the apoplastic pathway is abruptly blocked in the endodermis.
6. Describe the passage of water from the root hair to the xylem.

Learning Activity 5

Answer the following questions in your exercise book.

1. Study Fig. 7.29 on p.146.
   1. What is the purpose of the root cap?
   2. What is the purpose of the root hair?
   3. How does water enter the root hair from the soil?
2. Explain the water potential difference between soil water and the cytoplasm and cell sap inside the root hair.
3. Describe the mutualism between some plants and fungi.
4. Draw an annotated diagram (similar to Fig. 7.14) where you summarize how water moves through the root hair to the xylem, up the xylem to the leaf and out through the leaf. Give as much information as you can. [Note: This could be a useful diagram to use for revising this section before the exam. In your annotation refer to when water diffuses and when it evaporates.]

Mindmap

Add this section to your chapter seven mind map.