BIOL180 Lesson 9 Quiz Plant
Structure and Function Questions And
Correct Answers (Verified Answers)
Plus Rationales 2026 Q&A | Instant
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1. Which structure is primarily responsible for protecting the growing
tip of a plant root as it pushes through soil?
A. Pericycle
B. Endodermis
C. Root cap
D. Vascular cambium
Answer: C. Root cap
Rationale: The root cap protects the delicate apical meristem at the root
tip from abrasion as the root grows through soil. Its cells can be
sloughed off and replaced continuously. The root cap also participates
in sensing gravity, helping roots orient their growth downward. The
endodermis regulates movement into the vascular cylinder, while the
pericycle contributes to lateral root formation. Vascular cambium is a
lateral meristem involved primarily in secondary growth.
2. Which plant tissue is responsible for most of the photosynthesis
occurring in a typical leaf?
A. Mesophyll
B. Epidermis
,C. Xylem
D. Cork
Answer: A. Mesophyll
Rationale: Mesophyll tissue contains abundant chloroplasts and is
therefore the primary photosynthetic tissue in most leaves. It is
commonly divided into palisade mesophyll and spongy mesophyll.
Palisade cells are particularly efficient at capturing light, while spongy
mesophyll has extensive air spaces that facilitate gas exchange.
Epidermal cells mainly provide protection, xylem transports water, and
cork provides protection in woody plants.
3. What is the primary function of xylem tissue?
A. Transporting sugars from sources to sinks
B. Producing reproductive cells
C. Regulating stomatal opening
D. Transporting water and dissolved minerals upward
Answer: D. Transporting water and dissolved minerals upward
Rationale: Xylem conducts water and mineral ions absorbed by roots
toward stems and leaves. Much of the conducting tissue consists of
dead, hollow cells such as vessel elements and tracheids, which form
continuous pathways. Transpiration, cohesion, adhesion, and tension
contribute to the upward movement of water. Phloem, rather than
xylem, transports sugars and other organic compounds throughout the
plant.
4. Which cells directly regulate the opening and closing of stomata?
A. Companion cells
B. Guard cells
,C. Root hairs
D. Sieve-tube elements
Answer: B. Guard cells
Rationale: Guard cells surround each stomatal pore and control its
opening and closing by changing their turgor pressure. When guard
cells gain water and become turgid, the pore generally opens; when
they lose water and become less turgid, it closes. This regulation
balances carbon dioxide uptake for photosynthesis with the need to
minimize water loss through transpiration.
5. Which plant tissue is considered a meristematic tissue?
A. Apical meristem
B. Sclerenchyma
C. Xylem
D. Phloem
Answer: A. Apical meristem
Rationale: Apical meristems contain actively dividing cells and are
responsible for primary growth, which increases the length of roots
and shoots. They are located near the tips of roots and shoots.
Sclerenchyma, xylem, and phloem are mature tissues rather than
meristematic tissues. Other meristems, such as vascular cambium and
cork cambium, contribute to secondary growth.
6. Which tissue transports carbohydrates such as sucrose from
photosynthetic tissues to other parts of the plant?
A. Xylem
B. Epidermis
C. Phloem
D. Collenchyma
, Answer: C. Phloem
Rationale: Phloem transports sugars and other organic nutrients from
source tissues to sink tissues. Mature leaves commonly act as sources
because they produce sugars through photosynthesis, while roots,
developing fruits, seeds, and growing tissues can function as sinks.
Sieve-tube elements are the principal conducting cells of phloem and
are associated with companion cells.
7. What is the main advantage of root hairs to a plant?
A. They produce flowers.
B. They prevent all water loss.
C. They transport sugars directly to leaves.
D. They increase the surface area available for absorption.
Answer: D. They increase the surface area available for absorption.
Rationale: Root hairs are extensions of epidermal cells that greatly
increase the surface area of the root in contact with soil. This
improves the plant's ability to absorb water and mineral ions. Root
hairs are especially important near young portions of roots. They do
not primarily transport sugars, produce flowers, or prevent water loss
from the entire plant.
8. Which tissue provides flexible structural support to growing plant
organs?
A. Collenchyma
B. Sclerenchyma
C. Xylem
D. Phloem
Answer: A. Collenchyma
Structure and Function Questions And
Correct Answers (Verified Answers)
Plus Rationales 2026 Q&A | Instant
Download Pdf
1. Which structure is primarily responsible for protecting the growing
tip of a plant root as it pushes through soil?
A. Pericycle
B. Endodermis
C. Root cap
D. Vascular cambium
Answer: C. Root cap
Rationale: The root cap protects the delicate apical meristem at the root
tip from abrasion as the root grows through soil. Its cells can be
sloughed off and replaced continuously. The root cap also participates
in sensing gravity, helping roots orient their growth downward. The
endodermis regulates movement into the vascular cylinder, while the
pericycle contributes to lateral root formation. Vascular cambium is a
lateral meristem involved primarily in secondary growth.
2. Which plant tissue is responsible for most of the photosynthesis
occurring in a typical leaf?
A. Mesophyll
B. Epidermis
,C. Xylem
D. Cork
Answer: A. Mesophyll
Rationale: Mesophyll tissue contains abundant chloroplasts and is
therefore the primary photosynthetic tissue in most leaves. It is
commonly divided into palisade mesophyll and spongy mesophyll.
Palisade cells are particularly efficient at capturing light, while spongy
mesophyll has extensive air spaces that facilitate gas exchange.
Epidermal cells mainly provide protection, xylem transports water, and
cork provides protection in woody plants.
3. What is the primary function of xylem tissue?
A. Transporting sugars from sources to sinks
B. Producing reproductive cells
C. Regulating stomatal opening
D. Transporting water and dissolved minerals upward
Answer: D. Transporting water and dissolved minerals upward
Rationale: Xylem conducts water and mineral ions absorbed by roots
toward stems and leaves. Much of the conducting tissue consists of
dead, hollow cells such as vessel elements and tracheids, which form
continuous pathways. Transpiration, cohesion, adhesion, and tension
contribute to the upward movement of water. Phloem, rather than
xylem, transports sugars and other organic compounds throughout the
plant.
4. Which cells directly regulate the opening and closing of stomata?
A. Companion cells
B. Guard cells
,C. Root hairs
D. Sieve-tube elements
Answer: B. Guard cells
Rationale: Guard cells surround each stomatal pore and control its
opening and closing by changing their turgor pressure. When guard
cells gain water and become turgid, the pore generally opens; when
they lose water and become less turgid, it closes. This regulation
balances carbon dioxide uptake for photosynthesis with the need to
minimize water loss through transpiration.
5. Which plant tissue is considered a meristematic tissue?
A. Apical meristem
B. Sclerenchyma
C. Xylem
D. Phloem
Answer: A. Apical meristem
Rationale: Apical meristems contain actively dividing cells and are
responsible for primary growth, which increases the length of roots
and shoots. They are located near the tips of roots and shoots.
Sclerenchyma, xylem, and phloem are mature tissues rather than
meristematic tissues. Other meristems, such as vascular cambium and
cork cambium, contribute to secondary growth.
6. Which tissue transports carbohydrates such as sucrose from
photosynthetic tissues to other parts of the plant?
A. Xylem
B. Epidermis
C. Phloem
D. Collenchyma
, Answer: C. Phloem
Rationale: Phloem transports sugars and other organic nutrients from
source tissues to sink tissues. Mature leaves commonly act as sources
because they produce sugars through photosynthesis, while roots,
developing fruits, seeds, and growing tissues can function as sinks.
Sieve-tube elements are the principal conducting cells of phloem and
are associated with companion cells.
7. What is the main advantage of root hairs to a plant?
A. They produce flowers.
B. They prevent all water loss.
C. They transport sugars directly to leaves.
D. They increase the surface area available for absorption.
Answer: D. They increase the surface area available for absorption.
Rationale: Root hairs are extensions of epidermal cells that greatly
increase the surface area of the root in contact with soil. This
improves the plant's ability to absorb water and mineral ions. Root
hairs are especially important near young portions of roots. They do
not primarily transport sugars, produce flowers, or prevent water loss
from the entire plant.
8. Which tissue provides flexible structural support to growing plant
organs?
A. Collenchyma
B. Sclerenchyma
C. Xylem
D. Phloem
Answer: A. Collenchyma
