Plant Adaptations and Responses
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.
Critical Reading
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.
Questions
1. What is a main challenge faced by plants that live in a desert?
2. Name three strategies used by xerophytes to adapt to their environment.
3. In what type of environment does a saguaro cactus live?
4. How does the saguaro cactus take advantage of rare, brief rainfall?
5. How does the structure of the saguaro cactus stem benefit the plant?
Multiple Choice
Circle the letter of the correct choice.
1. Which of the following is not a typical characteristic of aquatic plants?
(a) They live in the water.
(b) They have extensive vascular tissues for transporting water.
(c) Their leaves collect sunlight. (d) They do not need roots.
2. Desert plants adapt to a limited water supply by
(a) conserving water.
(b) storing water.
(c) efficiently absorbing water when it is available.
(d) all of the above
3. Which of the following plants is an epiphyte?
(a) orchid
(b) saguaro cactus
(c) cattail
(d) water lily
4. Which kind of plant is best adapted for life in the tropical rainforest?
(a) saguaro cactus
(b) epiphyte
(c) oak tree
(d) all of the above
5. The leaves of which plant are shaped to collect and store a lot of water?
(a) water lily
(b) cattail
(c) saguaro cactus
(d) bromeliad
6. Growth toward the force of gravity is called
(a) auxin.
(b) geotropism.
(c) phototropism.
(d) thigmotropism.
7. Growth toward the light is called
(a) auxin.
(b) geotropism.
(c) phototropism.
(d) thigmotropism.
8. Plants often enter dormancy
(a) when rainfall is abundant.
(b) just before they form flowers.
(c) during winter.
(d) in the spring.
Vocabulary I
Match the vocabulary word with the proper definition.
Definitions
_____ 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
Terms
a. aquatic
b. auxin
c. epiphyte
d. geotropism
e. herbivore
f. photosynthesis
g. phototropism
h. temperate
i. transpiration
j. tropical
k. tropism
l. xerophyte
Vocabulary II
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 ________.
Critical Writing
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?