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Answers to End-of-Chapter Questions – Brooker et al ARIS site
Chapter 35
Test Yourself Questions
1. Where would you look to find the gametophyte generation of a flowering plant?
a. at the shoot apical meristem
b. at the root apical meristem
c. in seeds
d. in flower parts
e. none of the above
Answer: d. The microscopic male and female gametophytes, which produce sperm and eggs, are
located within flower organs.
2. What is a radicle?
a. an embryonic leaf
b. an embryonic stem
c. an embryonic root
d. a mature root system of a monocot
e. an organism that has extreme political views
Answer: c. A radicle (note spelling) is an embryonic root.
3. What is the correct term for a plant that does not reproduce in its first year of life, but often produces
flowers and seeds within the following year?
a. an annual
b. a biennial
c. a perennial
d. a centennial
e. none of the above
Answer: b. A biennial is a plant that does not reproduce until the second year of life at the earliest.
4. Which of the following terms best describe the distinctive architecture of plants?
a. radial symmetry and apical-basal polarity
b. bilateral symmetry and apical-basal polarity
c. radial symmetry and absence of apical-basal polarity
d. bilateral symmetry and absence of apical-basal polarity
e. absence of symmetry and absence of apical-basal polarity
Answer: a. Plant architecture is characterized by radial symmetry and apical-basal polarity.
5. Which is the most accurate description of how plants grow?
a. by the addition of new cells at meristems that include stem cells
b. by cell enlargement as the result of water uptake
c. by both the addition of new cells and cell expansion
d. by addition of fat cells
e. none of the above
Answer: c. Plants grow by both the addition of new cells at meristems (which involve stem cells) and by
cell expansion as the result of water uptake.
6. Where would you look for leaf primordia?
a.
b.
c.
d.
e.
at a vegetative shoot tip
at the root apical meristem
at the vascular cambium
at the cork cambium
in a floral bud
Answer: a. Leaf primordia are produced at vegetative shoot apical meristems.
7. Which leaf tissues display the greatest amount of air space?
a. the adaxial epidermis
b. the abaxial epidermis
c. the palisade parenchyma
d. the spongy parenchyma
e. the vascular tissues
Answer: d. The spongy parenchyma is named for its abundant air spaces, which facilitate carbon
dioxide absorption by photosynthetic cells of the leaf.
8. What is an adventitious root?
a. roots that develop on plant cuttings that have been placed in water
b. buttress roots that grow from tree trunks
c. the only kinds of roots produced by monocots, because their embryonic root dies soon after
seed germination
d. any root that is produced by stem (or sometimes leaf) tissue, rather than developing directly
from the embryonic root
e. all of the above
Answer: e. An adventitious root is one that is produced by stem or leaf tissue; examples include the root
systems of monocots, roots that grow on plant cuttings, and buttress roots.
9. During its development, a tracheid will elongate in a direction parallel to the shoot or root axis.
Based on this information, what can you say about the orientation of cellulose cell-wall microfibrils
and cytoplasmic microtubules in this developing tracheid?
a. The microfibrils will be oriented perpendicularly (at right angles) to the long axis of the
developing tracheid, encircling it, but the cytoplasmic microtubules will be oriented parallel
to the direction in which the tracheid is elongating.
b. Microfibrils and microtubules will both be oriented perpendicularly (at right angles) to the
elongating axis of the tracheid.
c. Microfibrils and microtubules will both be oriented parallel to the direction of tracheid
elongation.
d. Microfibrils will be oriented parallel to the direction of tracheid elongation, but microtubules
will be perpendicular (at right angles) to both the microfibrils and the elongating tracheid.
e. None of the above.
Answer: b. Microtubules influence the direction in which microfibrils are synthesized, such that they
have the same orientation. The encircling microfibrils restrict cell expansion to the direction
perpendicular to microfibril orientation. Recall the example of tape bands on an inflating balloon.
10. What are examples of woody plants?
a. trees
b. shrubs
c. woody vines, known as lianas
d. all of the above
e. none of the above
Answer: d. Trees, shrubs, and woody vines (lianas) are the three types of woody plants.
Conceptual Questions
1. What would be the consequences if overall plant architecture were bilaterally symmetrical?
Answer: Plants would be shaped like higher animals, with a distinct front (ventral surface) and back
(dorsal surface). By comparison to radially symmetrical organisms, bilaterally symmetrical plants would
have reduced ability to deploy branches and leaves in a way that would fill available lighted space, and
would thus not be able to take optimal photosynthetic advantage of their habitats.
2. What would be the consequences if leaves were radially symmetrical (shaped like spheres or
cylinders)?
Answer: In a radially symmetrical form, leaves would not have maximal ability to absorb sunlight, and
they would not be able to optimally disperse excess heat from their surfaces.
3. Why are most tall plants also woody, rather than herbaceous?
Answer: Although tall herbaceous plants exist (palms and bamboo are examples), the additional support
and water-conducting capacity that is provided by secondary xylem allow woody plants to grow tall.
Experimental Questions
1. Why did Elle and colleagues begin their investigation by growing Datura wrightii plants from seeds
in a greenhouse?
Answer: By doing so, they were able to start with a fairly uniform population of experimental plants that
were mature enough to have developed defensive features such as trichomes. If they had started the
plants outdoors, many of the seedlings could have been lost to drought or other stresses at an early
stage in the experiment.
2. Why did Elle and colleagues move the mature plants outdoors, but treat only half of them with
herbicide?
Answer: Outdoors the plants were exposed to normal selective pressures, such as herbivorous (planteating) insects. By spraying some of the plants (and thereby removing the impact of insect herbivores)
the investigators could compare the success of plants having different types of trichomes under
conditions in which herbivores were present or absent.
3. Why did the investigators keep track of plant growth as well as plant reproduction during the
experiment?
Answer: By so doing, the experimenters were able to observe the protective effect of sticky trichomes, a
result that would not have been observed had they only monitored seed production.
Collaborative Questions
1. Find a tree stump or a large limb that has recently been cut from a tree (or imagine doing so). Which
of the following features could you locate with the unaided eye: the outer bark, the inner bark, the
secondary xylem, the vascular cambium, annual rings?
Answer: You would be able to locate the outer bark, secondary xylem, and annual rings, but the inner
bark and vascular cambium would likely be too thin for you to see without the use of a microscope.
2. Which physical factors would you expect influence shoot growth most strongly? Which physical
factors would you expect most strongly influence underground root growth?
Answer: You would expect shoot growth to be particularly responsive to light, humidity, temperature,
wind, and carbon dioxide concentration, because these physical factors influence photosynthesis. You
would expect soil water, soil minerals, obstructing soil particles (such as rocks), and gravity to most
strongly affect the growth of underground root systems.