Part 4 — Secondary Growth: Vascular Cambium, Secondary Xylem/Phloem, Periderm (Questions 76–100)

Q76. The vascular cambium is a meristematic layer producing:

A) Only cork
B) Secondary xylem (wood) inward and secondary phloem outward leading to increase in girth
C) Apical dominance hormones only
D) Leaf primordia
Answer: B
Explanation:

B) Correct — primary function of vascular cambium.
A/C/D) Wrong.

Q77. Early wood (spring wood) is characterized by:

A) Small vessels and thick walls
B) Large vessel elements with thin walls produced during favorable growth season, forming less dense wood
C) No vessels at all
D) Only rays present
Answer: B
Explanation:

B) Correct — early wood has large conduits for rapid water transport.
A/C/D) Incorrect.

Q78. Heartwood differs from sapwood in that heartwood:

A) Is active in water conduction
B) Is dead, darker, impregnated with extractives and resistant to decay; sapwood is active in conduction and lighter in color
C) Is always lighter colored
D) Contains living parenchyma conducting sugars
Answer: B
Explanation:

B) Correct — heartwood is non-conducting, stores extractives.
A/C/D) False.

Q79. Rays in secondary xylem are:

A) Axial elements only
B) Parenchymatous radial files that serve in radial conduction and storage (medullary rays)
C) Only in leaves
D) Epidermis
Answer: B
Explanation:

B) Correct — rays conduct radially and store substances.
A/C/D) Incorrect.

Q80. Cork cambium (phellogen) produces:

A) Xylem inward only
B) Cork (phellem) outward and phelloderm inward forming periderm for protection and reducing water loss
C) Phloem outward only
D) Only epidermis
Answer: B
Explanation:

B) Correct — phellogen makes cork and phelloderm.
A/C/D) Wrong.

Q81. Which best describes lenticel function?

A) They are openings in periderm enabling gas exchange between internal tissues and atmosphere in woody stems/roots
B) They function in water conduction into stele
C) They produce flowers
D) They perform photosynthesis exclusively
Answer: A
Explanation:

A) Correct — lenticels allow gaseous exchange.
B/C/D) False.

Q82. In dicot wood, vessels are arranged in:

A) Scattered manner only as in monocots
B) Rings or diffuse patterns forming ring-porous or diffuse-porous wood depending on species (ring-porous early large vessels vs diffuse small vessels)
C) No vessels; only tracheids in all dicots
D) Only in phloem
Answer: B
Explanation:

B) Correct — vessel distribution varies, giving ring-porous/diffuse-porous patterns.
A/C/D) Not generally true.

Q83. Bark of a tree includes:

A) Only outermost cork
B) All tissues external to the vascular cambium: secondary phloem, cortex (if present), periderm (phellogen + phellem + phelloderm) — inner & outer bark included
C) Only xylem
D) Only leaves attached
Answer: B
Explanation:

B) Correct — bark = everything external to vascular cambium.
A/C/D) Incorrect.

Q84. The annual rings in temperate trees result from:

A) Differences in cell size and wall thickness of xylem formed in early (spring) vs late (summer) season due to climatic changes
B) Random wood deposition only
C) Presence of stomata rings
D) Leaf drop only
Answer: A
Explanation:

A) Correct — seasonal cambial activity causes rings.
B/C/D) Not the cause.

Q85. Tyloses formation in heartwood occurs by:

A) Outgrowths of parenchyma into vessels, blocking them to prevent water flow and pathogen entry, common in hardwoods like oak
B) Companion cell activity only
C) Formation in phloem only
D) Epidermal cell division
Answer: A
Explanation:

A) Correct — tyloses occlude vessels in heartwood.
B/C/D) Incorrect.

Q86. Which of these is a typical sequence during secondary growth?

A) Periderm forms before vascular cambium activity
B) Vascular cambium forms → secondary xylem/phloem laid down → cork cambium forms → periderm replaces epidermis
C) Leaves develop into periderm
D) Stomata become cambium
Answer: B
Explanation:

B) Correct sequence.
A/C/D) Not correct.

Q87. In woody plants, lenticels are formed as a result of:

A) Rapid division of cork cambium producing loosely packed cells that rupture periderm outwards forming lenticels
B) Formation of stomata on bark only
C) Xylem vessel rupture only
D) Root hair proliferation
Answer: A
Explanation:

A) Correct.
B/C/D) Wrong.

Q88. The inner bark of a tree comprises:

A) Secondary phloem (active in conduction of products of photosynthesis), some cortex, periderm? inner bark is living phloem and associated tissues
B) Secondary xylem only
C) Epidermis only
D) Only pericycle
Answer: A
Explanation:

A) Correct — inner bark = living phloem and cells outside cambium.
B/C/D) Incorrect.

Q89. Anomalous secondary growth (e.g., in Nyctanthes or Boerhavia) indicates:

A) Uniform cambial activity only as in normal dicots
B) Irregular activity of cambium or presence of additional cambia giving unique secondary growth patterns distinct from typical dicot wood formation
C) No cambium at all
D) Only primary growth occurs
Answer: B
Explanation:

B) Correct — anomalous cambial activity yields unusual secondary structures.
A/C/D) Not describing anomaly.

Q90. Suberin is mainly deposited in:

A) Chloroplasts of mesophyll
B) Cork cell walls imparting impermeability; also in Casparian strips in endodermis
C) Nucleus only
D) Sieve plates only
Answer: B
Explanation:

B) Correct — suberin (waxy compound) produces water-impermeable barriers.
A/C/D) False.

Q91. Secondary phloem is produced by:

A) Cork cambium only
B) Vascular cambium outward production; secondary phloem lies external to cambium and transports organic solutes
C) Epidermis only
D) Xylem cambium only
Answer: B
Explanation:

B) Correct.
A/C/D) Incorrect.

Q92. Which of the following contributes to formation of vascular cambium in stem?

A) Procambium in vascular bundles and parenchyma between bundles (interfascicular cambium) becoming meristematic
B) Epidermis only
C) Leaf primordia
D) Root cap
Answer: A
Explanation:

A) Correct.
B/C/D) Incorrect.

Q93. In secondary xylem, radial conduction is primarily via:

A) Tracheids only
B) Rays (parenchyma) performing radial translocation of water/solutes and storage
C) Epidermis only
D) Guard cells
Answer: B
Explanation:

B) Correct — rays important in radial conduction.
A/C/D) Not main radial conduits.

Q94. Which cambium derivative forms axial system of wood?

A) Rays only
B) Fusiform initials produce axial elements — vessels, tracheids, fibers in secondary xylem — constituting axial system
C) Epidermis
D) Collenchyma
Answer: B
Explanation:

B) Correct — fusiform initials give axial elements.
A/C/D) Wrong.

Q95. Bark includes all tissues external to vascular cambium; cork forms outermost protective layer. Which tissue lies immediately outside vascular cambium in a woody stem?

A) Secondary phloem (inner bark)
B) Secondary xylem (wood)
C) Epidermis always
D) Pith
Answer: A
Explanation:

A) Correct — phloem is external to cambium, xylem is internal.
B/C/D) Wrong.

Q96. Which of following statements about age determination in trees is true?

A) Count number of leaves on stem
B) Counting annual rings in secondary xylem (wood) gives approximate age in temperate climates — each ring usually corresponds to one year
C) Bark thickness always equals age exactly
D) Measure root length only
Answer: B
Explanation:

B) Correct — ring counting (dendrochronology) used to estimate age.
A/C/D) Not reliable.

Q97. Which cells participate in wound healing and callus formation in woody stems?

A) Fusiform initials only
B) Parenchyma cells dedifferentiate near wound and form callus; cork cambium may form to seal wound with periderm
C) Stomatal guard cells only
D) Chlorenchyma exclusively
Answer: B
Explanation:

B) Correct — parenchyma forms callus and cambial activity results in wound periderm.
A/C/D) Incorrect.

Q98. A tree shows wide early wood but very narrow late wood in a particular year — this implies:

A) Drought conditions during spring only
B) Favorable wet/warmer spring for cambial activity producing large vessels, followed by less favorable conditions — ring anatomy reflects seasonal growth conditions
C) No climatic influence
D) Continuous growth without seasons
Answer: B
Explanation:

B) Correct — environmental conditions affect ring anatomy.
A/C/D) Not fully explanatory.

Q99. Which of the following is NOT derived from vascular cambium?

A) Secondary xylem
B) Secondary phloem
C) Cork (phellem) — derived from cork cambium (phellogen), not vascular cambium
D) Secondary growth tissues in stems
Answer: C
Explanation:

C) Correct — cork comes from phellogen.
A/B/D) Derived from vascular cambium.

Q100. In ring-porous wood species, vessel distribution is:

A) Large vessels concentrated in early wood forming conspicuous rings; later wood has small vessels → ring-porous pattern
B) Evenly distributed vessels across ring (diffuse-porous)
C) No vessels at all
D) Vessels only in phloem
Answer: A
Explanation:

A) Correct — ring-porous anatomy feature.
B/C/D) Wrong.

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Part 4 — Secondary Growth: Vascular Cambium, Secondary Xylem/Phloem, Periderm (Questions 76–100)