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16.4: Plant Adaptations and Responses

Difficulty Level: At Grade Created by: CK-12
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Lesson 16.4: True or False

Name___________________ Class______________ Date________

Write true if the statement is true or false if the statement is false.

_____ 1. Aquatic plants have thick cuticles on their leaves.

_____ 2. Pollination is most effective when it happens under water.

_____ 3. Xerophytes are adapted to live in wet, rainy climates.

_____ 4. A saguaro cactus stores water in its thick stem.

_____ 5. A cactus is an epiphyte.

_____ 6. An orchid is an epiphyte.

_____ 7. Epiphytes grow on other plants mainly to avoid getting excess sunlight.

_____ 8. Some epiphytes absorb water from the air.

_____ 9. Some kinds of epiphytes can collect water in a tank-like structure.

_____ 10. Phototropism is growth of roots away from the light.

_____ 11. The tip of a plant grows toward a light source.

_____ 12. Some plants produce toxic chemicals that can kill pathogens.

_____ 13. Plants always respond to an infection with increased cell division and growth around the area of infection.

_____ 14. Plant hormones regulate growth in plants.

_____ 15. Because they cannot run away like animals can, plants cannot respond to environmental stimuli.

Lesson 16.4: Critical Reading

Name___________________ Class______________ Date________

Read these passages from the text and answer the questions that follow.

Adaptations to Extreme Dryness

Plants that live in extremely dry environments have the opposite problem: how to get and keep water. Plants that are adapted to very dry environments are called xerophytes. Their adaptations may help them increase water intake, decrease water loss, or store water when it is available.

The saguaro cactus pictured in Figure 16.24 in your book has adapted in all three ways. When it was still a very small plant, just a few inches high, its shallow roots already reached out as much as 2 meters (7 feet) from the base of the stem. By now, its root system is much more widespread. It allows the cactus to gather as much moisture as possible from rare rainfalls. The saguaro doesn’t have any leaves to lose water by transpiration. It also has a large, barrel-shaped stem that can store a lot of water. Thorns protect the stem from thirsty animals that might try to get at the water inside.


1. What is a main challenge faced by plants that live in a desert?

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2. Name three strategies used by xerophytes to adapt to their environment.

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3. In what type of environment does a saguaro cactus live?

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4. How does the saguaro cactus take advantage of rare, brief rainfall?

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5. How does the structure of the saguaro cactus stem benefit the plant?

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Lesson 16.4: Multiple Choice

Name___________________ Class______________ Date________

Circle the letter of the correct choice.

  1. Which of the following is not a typical characteristic of aquatic plants?
    1. They live in the water.
    2. They have extensive vascular tissues for transporting water.
    3. Their leaves collect sunlight.
    4. They do not need roots.
  2. Desert plants adapt to a limited water supply by
    1. conserving water.
    2. storing water.
    3. efficiently absorbing water when it is available.
    4. all of the above
  3. Which of the following plants is an epiphyte?
    1. orchid
    2. saguaro cactus
    3. cattail
    4. water lily
  4. Which kind of plant is best adapted for life in the tropical rainforest?
    1. saguaro cactus
    2. epiphyte
    3. oak tree
    4. all of the above
  5. The leaves of which plant are shaped to collect and store a lot of water?
    1. water lily
    2. cattail
    3. saguaro cactus
    4. bromeliad
  6. Growth toward the force of gravity is called
    1. auxin.
    2. geotropism.
    3. phototropism.
    4. thigmotropism.
  7. Growth toward the light is called
    1. auxin.
    2. geotropism.
    3. phototropism.
    4. thigmotropism.
  8. Plants often enter dormancy
    1. when rainfall is abundant.
    2. just before they form flowers.
    3. during winter.
    4. in the spring.

Lesson 16.4: Vocabulary I

Name___________________ Class______________ Date________

Match the vocabulary word with the proper definition.


_____ 1. movement toward or away from a stimulus

_____ 2. refers to regions near the equator

_____ 3. living in the water

_____ 4. growth toward a light source

_____ 5. an organism that uses plants as a food source

_____ 6. a growth hormone in plants

_____ 7. not too cold or hot; free from extremes in climate

_____ 8. a plant adapted to a very dry climate

_____ 9. growth in the same direction as the force of gravity

_____ 10. evaporative loss of water from leaves or stems

_____ 11. transformation of light energy, water, and carbon dioxide into chemical energy contained in sugars

_____ 12. a plant that grows on another plant


a. aquatic

b. auxin

c. epiphyte

d. geotropism

e. herbivore

f. photosynthesis

g. phototropism

h. temperate

i. transpiration

j. tropical

k. tropism

l. xerophyte

Lesson 16.4: Vocabulary II

Name___________________ Class______________ Date________

Fill in the blank with the appropriate term.

1. Plants that grow near the equator are all ________ plants.

2. ________ do not need roots because they get support and anchoring from another plant.

3. Cells on the dark side of a plant stem elongate in response to the plant growth hormone ________.

4. Plants make their own food by ________.

5. Movement toward or away from a stimulus is a ________.

6. ________ is evaporation of water vapor from the leaves, and sometimes stem of a plant.

7. A ________ climate is not extremely hot or cold.

8. ________ is growth toward a light source.

9. An organism that eats plants is a(n) ________.

10. Roots grow downward due to ________.

11. ________ plants live in water.

12. Plants adapted to environments where there is little water are ________.

Lesson 16.4: Critical Writing

Name___________________ Class______________ Date________

Thoroughly answer the question below. Use appropriate academic vocabulary and clear and complete sentences.

If plants don't have an immune system like that of humans, how do they respond to pathogens?

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