Xerophytes
Laura Armstrong & Joe Wolfensohn
Teachers
Contents
Recall Questions
This topic requires prior knowledge of leaf adaptations and gas exchange processes in plants under normal conditions. You can test your knowledge on these below.
What is transpiration, and what factors affect its rate? (2 marks)
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Transpiration is the evaporation of water from plant leaves via the stomata.
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Factors affecting transpiration include temperature, humidity, wind speed, and light intensity.
How do stomata contribute to water loss in plants? (1 mark)
Stomata are pores in the leaves that lead to water loss through evaporation.
What is the role of the waxy cuticle in plant leaves? (1 mark)
The waxy cuticle is a waterproof layer of lipids on the leaf surface that reduces water loss by evaporation.
Topic Explainer Video
Check out this @JoeDoesBiology video that explains xerophytes or read the full notes below. Once you've gone through the whole note, try out the practice questions!
Xerophytes and Their Adaptations
What Are Xerophytes?
Xerophytes are plants adapted to survive in dry environments, such as deserts (cacti) or windy coastal areas (marram grass), where water availability is low.
Key Adaptations of Xerophytes
Xerophytes have evolved structural and physiological features to minimize water loss:
1. Thick Waxy Cuticle
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Reduces water loss by evaporation.
2. Reduced Number of Stomata
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Fewer openings for water to escape, therefore a smaller surface area for evaporation to occur from.
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Helps reduce transpiration rates.
3. Sunken Stomata
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Stomata are located in pits to trap humid air.
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This reduces the water potential gradient, reducing transpiration.
4. Hairs on the Leaf Surface
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Traps moisture around the stomata.
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This reduces the water potential gradient, reducing transpiration.
5. Rolled Leaves
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Stomata are enclosed within the rolled-up leaf.
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Protects against wind and maintains a reduced water potential gradient around the stomata and reduces transpiration.
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Common in marram grass and other plants in windy environments
6. Small, Needle-Like Leaves or Spines
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Reduces surface area for water loss.
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Common in cacti and other desert plants.
7. Deep Root Systems
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Reach deep underground water sources.
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Some plants also have widespread shallow roots to absorb surface moisture from rainfall quickly.
Key Terms
- Transpiration: The evaporation of water from plant leaves.
- Xerophytes: Plants adapted to arid environments.
- Stomata: Pores on leaves that control gas exchange and water loss.
- Waxy Cuticle: A waterproof layer that prevents excessive evaporation.
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Exam Tip
When explaining adaptations make sure to link each feature to its function and how it benefits the plant.
No answer provided.
Marram grass has deep root systems. Describe and explain three other adaptations of marram grass that reduce water loss. (3 marks)
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Thick waxy cuticle reduces evaporation by acting as a waterproof barrier
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Sunken stomata trap moist air, reducing the water potential gradient and transpiration rate
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Hairs on leaves trap moist air, reducing the water potential gradient and reducing transpiration
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Rolled leaves trap moist air around stomata, reducing the water potential gradient and reducing transpiration
Practice Question
Try to answer the practice question from the TikTok on your own, then watch the video to see how well you did!