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Introduction to the lesson
Water is vitally important to the plant. Without water the plant will wither up and die. The plant needs to be able to obtain water from its environment. It also needs to be able to give off water into the environment through transpiration. Why do you think a plant needs water?
Transport of water
Read the section “The transport of water” on p.134-135 of the text book.
Notes:
- Remember the properties of water as you learned in chapter 2.
- Water moves from regions of higher water potential to regions of lower water potential (cf. chapter 4).
- Water molecules have a high cohesion---in other words, they tend to stick to one another. Water, therefore, moves in long, unbroken columns through the vascular tissue in plants.
Transpiration
Read the section "From leaf to atmosphere - transpiration" p.135 and "Factors affecting transpiration" (p.136-139).
Learning Activity 1
Answer the following questions in your exercise book.
- Using the text and Fig. 7.14 (p.134), describe the process of transpiration, starting in the leaf. You will also need to consult Fig. 7.15 (p.135).
- Answer question 7.2 on p.135.
- Using Fig. 7.16 on p.136, describing five steps of how water moves through a leaf. Use the terms: transpiration, evaporation and diffusion at each point to indicate how the water moves at that stage.
- List four factors that affect transpiration and give a brief description of how each will affect transpiration.
- Answer questions 7.3-7.4 on p.136.
Practical Investigation
Complete the following exercises in your exercise book:
- Re-read the experiment in the purple box 7.2 on p.137-139 of your text book.
- Using the information on epidermal peels, suggest an experiment that would
- Compare upper and lower epidermis
- Compare monocots and dicots (upper and lower epidermis)
- Different parts of the same leaf (Are stomata more frequent near veins?)
- What would a stomata look like on a microscope slide?
- Describe an experiment using simple photometers, to investigate different factors that could influence the rate of transpiration
- Explain how to measure the surface area of the whole leaf using grids
- Answer Question 7.6 (a and b) on p.139 of your text book.
Xerophytes
Read the section entitled "Xerophytes" on p.140-141 of your text book.
Learning Activity 2
Answer the following questions in your exercise book.
- List some adaptations that xerophytes have made to their leaves in order to prevent water loss
- Study Fig. 7.21a and Fig. 7.22 on p.140.
- Make an annotated drawing using Figure 7.22 (annotated – means a descriptive diagram with labelling to show specific parts, highlight sections, or imply functions. this is usually drawn to a defined and/or specific scale or magnification and is meant to be as precise and accurate as possible.
- Answer Question 7.7 on p.141.
Definitions and review
Definitions
- Transpiration
- Humidity
- Xerophytes
Mindmap
Add this section to your chapter seven mindmap.