1. Fifteen years ago, your parents hung a swing from the lower branch of a large tree
growing in your yard. When you go and sit in it today, you realize it is exactly the
same height off the ground as it was when you first sat in it 15 years ago. The
reason the swing is higher off the ground not as the tree has grown is that—
a. the tree trunk is only showing secondary growth
b. the tree trunk is part of the primary growth system of the plant, but
elongation is no longer occurring in that part of the tree
c. trees lack apical meristems and so do not get taller
d. you are hallucinating, because it is impossible for the swing not to have
been raised off the ground as the tree grew
The correct answer is a—the tree trunk is only showing secondary growth
A. Answer a is correct. The mature region of the trunk is undergoing secondary
growth from lateral meristems. Trees grow taller from their apical meristems.
The correct answer is a—
B. Answer b is incorrect. Primary growth occurs at apical meristems. The mature
region of a tree shoot (i.e., the trunk) is showing secondary growth from lateral
meristems.
The correct answer is a—
C. Answer c is incorrect. Trees do grow taller from apical meristems.
The correct answer is a—
D. Answer d is incorrect.
2. A unique feature of plants is indeterminate growth. Indeterminate growth is
possible because—
a. meristematic regions for primary growth occur throughout the entire plant
body
b. all cell types in a plant often give rise to meristematic tissue
c. meristematic cells continually replace themselves
d. all cells in a plant continue to divide indefinitely
The correct answer is c—
A. Answer a in incorrect. Meristematic regions for primary growth only occur in
specific regions, namely the apical meristems.
The correct answer is c—
B. Answer b is incorrect. Once cells have differentiated, meristematic cells are not
produced from these cells.
The correct answer is c—meristematic cells continually replace themselves
C. Answer c is correct. Every division of a meristematic cell produces a
differentiated cell and another meristematic cell, thereby allowing for an
indefinite number of cell divisions.
The correct answer is c—
D. Answer d is incorrect. Most cells do not continue to divide; only the mersitematic
tissues do so.
3. If you were to relocate the pericycle of a plant root to the epidermal layer, how
would it affect root growth?
a. Secondary growth in the mature region of the root would not occur.
b. The root apical meristem would produce vascular tissue in place of dermal
tissue.
c. Nothing would change, because the pericycle is normally located near the
epidermal layer of the root.
d. Lateral roots would grow from the outer region of the root and fail to
connect with the vascular tissue.
The correct answer is d—
A. Answer a is incorrect. Secondary growth occurs from lateral meristems, not the
pericycle.
The correct answer is d—
B. Answer b is incorrect. Primary vascular tissue arises from the procambium region
of the primary meristem, not the pericycle.
The correct answer is d—
C. Answer c in incorrect. The pericycle is normally located inside the endoderm
layer, not near the epidermis.
The correct answer is d—Lateral roots would grow from the outer region of the root and
fail to connect with the vascular tissue.
D. Answer d is correct. Lateral roots form from growth in the pericycle and must be
connected with the vascular tissue in the stele of the root. If they grew from the
lateral region of the root they would not be connected with the root vascular
tissue.
4. In vascular plants, one difference between root and shoot systems is that—
a. root systems cannot undergo secondary growth
b. root systems undergo secondary growth, but do not form bark
c. root systems contain pronounced zones of cell elongation, whereas shoot
systems do not
d. root systems can store food reserves, whereas stem structures do not
The correct answer is c—
A. Answer a is incorrect. Root systems can undergo secondary growth.
The correct answer is c—
B. Answer b is incorrect. Root systems can produce bark, just like stem systems.
The correct answer is c—root systems contain pronounced zones of cell elongation,
whereas root systems do not
C. Answer c is correct. Roots, unlike shoots, have a zone of cell elongation.
The correct answer is c—
D. Answer d is incorrect. Modified stems, such a tubers, are designed to store food
reserves.
5. When you peel your potatoes for dinner, you are removing the majority of their—
a. dermal tissue
b. vascular tissue
c. ground tissue
d. only a and b are removed with the peel
e. all of these are removed with the peel
The correct answer is d—
A. Answer a is incorrect. Although dermal tissue covers the outermost surface of
plant organs, this is not the only answer.
The correct answer is d—
B. Answer b is incorrect. Although potatoes are modified shoots and as such have
rings of vascular tissue close to the surface, this is not the only answer.
The correct answer is d—
C. Answer c is incorrect. Potatoes are composed mostly of ground tissue
(parenchyma) for storing starch reserves. Removing the outer layers of tissue
leaves this ground tissue behind.
The correct answer is d—only a and b are removed with the peel
D. Answer d is correct. Both dermal and ground tissue are removed when you peel a
potato.
6. You can determine the age of an oak tree by counting the annual rings of
_______________ formed by the __________________.
a. primary xylem; apical meristem
b. secondary phloem; vascular cambium
c. dermal tissue; cork cambium
d. secondary xylem; vascular cambium
The correct answer is d—
A. Answer a is incorrect. Primary xylem is functional only in the immature region of
a plant shoot. In older trees, secondary growth takes place in the shoot, and the
vascular cambium deposits rings of vascular tissue.
The correct answer is d—
B. Answer b is incorrect. The secondary phloem is deposited on the external side of
the vascular cambium. The older phloem tissue is crushed against the periderm
and eventually is shed.
The correct answer is d—
C. Answer c is incorrect. Dermal tissue covers the outermost surface of the tree
trunk. As the tree grows in girth, the dermal tissue splits and is repaired by the
cork cambium.
The correct answer is d—secondary xylem; vascular cambium
D. Answer d is correct. Secondary xylem is deposited on the internal side of the
vascular cambium. The production of xylem occurs constantly, but the size of
xylem elements changes with the seasons, giving the appearance of annual rings.
7. Many vegetables are grown today through hydroponics, where the plant roots
exist primarily in an aqueous solution. Which of the following root structures is
no longer beneficial in hydroponics?
a. Epidermis
b. Xylem
c. Root cap
d. Root hairs
The correct answer is c—
A. Answer a is incorrect. The epidermis would still function in nutrient and water
uptake, as well as protection from pathogens.
The correct answer is c—
B. Answer b is incorrect. The roots would still require xylem for water and nutrient
transport to the stem.
The correct answer is c—Root cap
C. Answer c is correct. The root cap would not serve an immediate protective
purpose in the absence of soil.
The correct answer is c—
D. Answer d is incorrect. The root hairs would still provide increased surface area for
water and nutrient uptake.
8. Root hairs and lateral roots are similar in each respect except—
a. both increase the absorptive surface area of the root system
b. both are generally long-lived
c. both are multicellular
d. b and c
The correct answer is d—
A. Answer a is incorrect. Both increase the absorptive area of the root.
The correct answer is d—
B. Answer b is correct. Root hairs, unlike lateral roots, are fairly short-lived.
The correct answer is d—
C. Answer c is correct. Root hairs are not multicellular, but are extensions of an
epidermal cell.
The correct answer is d—both b and c
D. Answer d is correct. Both b and c are correct.
9. Which of the following statements is NOT true of the stems of vascular plants?
a. Stems are composed of repeating segments, including nodes and
internodes.
b. Primary growth only occurs at the shoot apical meristem.
c. Vascular tissues may be arranged on the outside of the stem or scattered
throughout the stem.
d. Stems can contain stomata.
The correct answer is b—
A. Answer a is incorrect. Plant stems are developed from repeating segments.
The correct answer is b—Primary growth only occurs at the shoot apical meristem.
B. Answer b is correct. Primary growth can also occur from axillary buds.
The correct answer is b—
C. Answer c is incorrect. Vascular tissues can be arranged throughout the stem
(monocots) or on the outside of the stem (eudicots).
The correct answer is b—
D. Answer d is incorrect. Many stems do contain stomata.
10. Plant organs form by—
a. cell division in gamete tissue
b. cell division in meristematic tissue
c. cell migration into the appropriate position in the tissue
d. rearranging the genetic material in the precursor cells so that the organspecific genes are activated
The correct answer is b—
A. Answer a is incorrect. Gametes are required for fertilization but not
morphogenesis in plants.
The correct answer is b—cell division in meristematic tissue
B. Answer b is correct. All plant cells arise by cell division in meristems.
The correct answer is b—
C. Answer c is incorrect. Plant cells do not move within the organism.
Morphogenesis in plants is growth-dependant.
The correct answer is b—
D. Answer d is incorrect. Activating organ-specific gene expression does not involve
rearranging the genetic material, but rather requires specific transcription factors
in the precursor cells.
11. Which of the following plant cell type is mismatched to its function?
a. Xylem; conducts mineral nutrients.
b. Phloem; serves as part of the bark.
c. Trichomes; reduces evaporation.
d. Collenchyma; performs photosynthesis.
The correct answer is d—
A. Answer a is incorrect. It is properly matched as the primary role of xylem is to
conduct water and mineral nutrients.
The correct answer is d—
B. Answer b is incorrect. It is properly matched as phloem is considered part of the
bark.
The correct answer is d—
C. Answer c is incorrect. It is properly matched as one primary function of
trichomes is to reduce leaf temperatures, and hence limit evaporation rates from
leaves.
The correct answer is d—Collenchyma; performs photosynthesis.
D. Answer d is correct. It is incorrectly matched, as parenchyma cells, not
collenchyma, serve for photosynthesis.
12. Which is the correct sequence of cell types encountered in an oak tree, moving
from the center of the tree out?
a. Pith, secondary xylem, primary xylem, vascular cambium, primary
phloem, secondary phloem, cork cambium, cork.
b. Pith, primary xylem, secondary xylem, vascular cambium, secondary
phloem, primary phloem, cork cambium, cork
c. Pith, primary xylem, secondary xylem, vascular cambium, secondary
phloem, primary phloem, cork, cork cambium
d. Pith, primary phloem secondary phloem, vascular cambium, secondary
xylem, primary xylem, cork cambium, cork.
The correct answer is b—
A. Answer a is incorrect. The primary and secondary xylem and phloem are in the
wrong order.
The correct answer is b—Pith, primary xylem, secondary xylem, vascular cambium,
secondary phloem, primary phloem, cork cambium, cork
B. Answer b is correct.
The correct answer is b—
C. Answer c is incorrect. The cork and cork cambium are reversed.
The correct answer is b—
D. Answer D is incorrect. The xylem and phloem are each on the wrong side of the
vascular cambium.
13. You’ve just bought a house with a great view of the mountains, but you have a
neighbor who planted a bunch of trees which are now blocking your view. In an
attempt to ultimately remove the trees and remain unlinked to the deed, you begin
training several porcupines to enter the yard under the cover of night and perform
a stealth operation. In order to most effectively kill the trees, you should train the
porcupines to completely remove—
a. the vascular cambium
b. the cork
c. the cork cambium
d. the primary phloem
The correct answer is a—the vascular cambium
A. Answer a is correct. Removal of the vascular cambium would eliminate the ability
to produce any more xylem or phloem cells, thereby causing death.
The correct answer is a—
B. Answer b is incorrect. A tree could reform more cork from the cork cambium.
The correct answer is a—
C. Answer c is incorrect. A tree could technically still survive without the production
of bark, though it would be significantly weakened.
The correct answer is a—
D. Answer d is incorrect. Most primary phloem will not be functional in a tree,
unlike the secondary phloem.
Challenge Questions
1. Plant organs undergo many modifications to deal with environmental challenges.
Define your favorite modified root, shoot, and leaf, and make a case for why it is
the best example of a modified plant organ.
Answer—There are many ways to answer this question, as long as you specify which
organ is modified, describe the modification, and make your case that the modification
provides a solution to an environmental challenge. To answer this question, start by
reviewing examples of modified roots, modified stems, and modified leaves. If you
choose pneumatophores, for example, explain that these are modified root outgrowths of
submerged roots. These modified roots extend above the surface of the water, allowing
the plant to obtain enough oxygen to survive.
2. You design a grand scheme to construct a “super plant” that can increase
photosynthetic productivity well above normal levels. To do this, you pack the
leaves with palisade parenchyma (mesophyll) cells. Would this increase the
photosynthetic productivity of a leaf? Why or why not?
Answer—Increasing the number of mesophyll cells, the site of photosynthesis, could
increase photosynthetic productivity. There are, however, many other factors to consider.
Photosynthesis requires sufficient gas exchange and water. If you do not increase the
stomata on the surface of the leaves the rate of photosynthesis is likely to be limited by
the availability of oxygen and the amount of water made available through transpiration.
Remember, it is the ratio of oxygen to carbon dioxide that affects the efficiency of
Rubisco, the key enzyme needed to fix carbon dioxide in the Calvin cycle (you can
review the biochemistry of photosynthesis in chapter 10 and look ahead for more
information on the affect of carbon dioxide on photosynthesis). In summary, you may
increase photosynthesis, but you might not have a “super plant.”
3. You have identified a mutant maize plant that cannot differentiate vessel cells.
How would this affect the functioning of the plant?
Answer—The mutant maize plant would not be able to transport enough water if vessel
cells failed to differentiate. As the plant grew, it would wilt, have stunted growth, and
perhaps not survive. Remember that there would be some water transport through the
tracheids, but this would not be sufficient.