ISA Certified Arborist Examination
Questions And Correct Answers
(Verified Answers) Plus Rationales
2026 Q&A | Instant Download Pdf
1. Which tissue is primarily responsible for producing new cells that
increase the diameter of a tree stem?
A. Phloem
B. Vascular cambium
C. Heartwood
D. Pith
B. Vascular cambium
Answer: B. Vascular cambium.
Rationale: The vascular cambium is a lateral meristem that produces
secondary xylem toward the inside and secondary phloem toward the
outside, allowing stems and roots to increase in diameter.
2. What is the primary function of xylem in a living tree?
A. Transporting sugars from leaves to roots
B. Producing hormones in the leaves
C. Conducting water and dissolved minerals
D. Storing all reserve carbohydrates
C. Conducting water and dissolved minerals
Answer: C. Conducting water and dissolved minerals.
,Rationale: Xylem conducts water and mineral nutrients primarily from
the roots toward the crown. Much of the conducting xylem is
composed of specialized cells that become nonliving at maturity.
3. Which process converts light energy into chemical energy in green
leaves?
A. Respiration
B. Photosynthesis
C. Transpiration
D. Fermentation
B. Photosynthesis
Answer: B. Photosynthesis.
Rationale: Photosynthesis uses light energy to convert carbon dioxide
and water into carbohydrates, releasing oxygen as a by-product. The
resulting carbohydrates provide energy and carbon skeletons for
growth and maintenance.
4. Which structure controls most gas exchange and water vapor loss
through a leaf?
A. Stoma
B. Cambium
C. Lenticel
D. Petiole
A. Stoma
Answer: A. Stoma.
Rationale: Stomata are microscopic pores, generally controlled by
guard cells, that regulate carbon dioxide entry and water vapor loss.
,Their opening and closing strongly influence photosynthesis and
transpiration.
5. What is transpiration?
A. Movement of sugars through phloem
B. Loss of water vapor from plant surfaces
C. Formation of annual growth rings
D. Conversion of starch into cellulose
B. Loss of water vapor from plant surfaces
Answer: B. Loss of water vapor from plant surfaces.
Rationale: Transpiration is the loss of water vapor, primarily through
stomata. It contributes to the movement of water through the plant and
helps maintain the water stream from roots to foliage.
6. Which tree structure is most closely associated with the transition
between the trunk and major roots?
A. Root collar
B. Terminal bud
C. Leaf scar
D. Crown shyness
A. Root collar
Answer: A. Root collar.
Rationale: The root collar, often associated with the trunk flare, is the
transition zone between the stem and root system. Proper identification
of this area is particularly important during planting and inspection.
7. What is compartmentalization of decay in trees?
A. Complete elimination of decay organisms
B. A tree's ability to restrict the spread of dysfunction and decay
, C. Rapid replacement of all damaged wood
D. Removal of dead branches by natural shedding
B. A tree's ability to restrict the spread of dysfunction and decay
Answer: B. A tree's ability to restrict the spread of dysfunction and
decay.
Rationale: Compartmentalization is the tree's biological response to
injury and infection. The tree forms boundaries that restrict the
movement of decay and dysfunction through tissues.
8. Which carbohydrate is commonly transported through phloem to
support growth and storage?
A. Cellulose
B. Sucrose
C. Lignin
D. Pectin
B. Sucrose
Answer: B. Sucrose.
Rationale: Sucrose is a principal form in which photosynthetically
produced carbohydrates are transported through the phloem from
source tissues to sinks such as roots, developing shoots, fruits, and
storage tissues.
9. Which root function is most directly associated with anchoring a
tree?
A. Producing chlorophyll
B. Providing mechanical stability
C. Producing flowers
D. Increasing transpiration
Questions And Correct Answers
(Verified Answers) Plus Rationales
2026 Q&A | Instant Download Pdf
1. Which tissue is primarily responsible for producing new cells that
increase the diameter of a tree stem?
A. Phloem
B. Vascular cambium
C. Heartwood
D. Pith
B. Vascular cambium
Answer: B. Vascular cambium.
Rationale: The vascular cambium is a lateral meristem that produces
secondary xylem toward the inside and secondary phloem toward the
outside, allowing stems and roots to increase in diameter.
2. What is the primary function of xylem in a living tree?
A. Transporting sugars from leaves to roots
B. Producing hormones in the leaves
C. Conducting water and dissolved minerals
D. Storing all reserve carbohydrates
C. Conducting water and dissolved minerals
Answer: C. Conducting water and dissolved minerals.
,Rationale: Xylem conducts water and mineral nutrients primarily from
the roots toward the crown. Much of the conducting xylem is
composed of specialized cells that become nonliving at maturity.
3. Which process converts light energy into chemical energy in green
leaves?
A. Respiration
B. Photosynthesis
C. Transpiration
D. Fermentation
B. Photosynthesis
Answer: B. Photosynthesis.
Rationale: Photosynthesis uses light energy to convert carbon dioxide
and water into carbohydrates, releasing oxygen as a by-product. The
resulting carbohydrates provide energy and carbon skeletons for
growth and maintenance.
4. Which structure controls most gas exchange and water vapor loss
through a leaf?
A. Stoma
B. Cambium
C. Lenticel
D. Petiole
A. Stoma
Answer: A. Stoma.
Rationale: Stomata are microscopic pores, generally controlled by
guard cells, that regulate carbon dioxide entry and water vapor loss.
,Their opening and closing strongly influence photosynthesis and
transpiration.
5. What is transpiration?
A. Movement of sugars through phloem
B. Loss of water vapor from plant surfaces
C. Formation of annual growth rings
D. Conversion of starch into cellulose
B. Loss of water vapor from plant surfaces
Answer: B. Loss of water vapor from plant surfaces.
Rationale: Transpiration is the loss of water vapor, primarily through
stomata. It contributes to the movement of water through the plant and
helps maintain the water stream from roots to foliage.
6. Which tree structure is most closely associated with the transition
between the trunk and major roots?
A. Root collar
B. Terminal bud
C. Leaf scar
D. Crown shyness
A. Root collar
Answer: A. Root collar.
Rationale: The root collar, often associated with the trunk flare, is the
transition zone between the stem and root system. Proper identification
of this area is particularly important during planting and inspection.
7. What is compartmentalization of decay in trees?
A. Complete elimination of decay organisms
B. A tree's ability to restrict the spread of dysfunction and decay
, C. Rapid replacement of all damaged wood
D. Removal of dead branches by natural shedding
B. A tree's ability to restrict the spread of dysfunction and decay
Answer: B. A tree's ability to restrict the spread of dysfunction and
decay.
Rationale: Compartmentalization is the tree's biological response to
injury and infection. The tree forms boundaries that restrict the
movement of decay and dysfunction through tissues.
8. Which carbohydrate is commonly transported through phloem to
support growth and storage?
A. Cellulose
B. Sucrose
C. Lignin
D. Pectin
B. Sucrose
Answer: B. Sucrose.
Rationale: Sucrose is a principal form in which photosynthetically
produced carbohydrates are transported through the phloem from
source tissues to sinks such as roots, developing shoots, fruits, and
storage tissues.
9. Which root function is most directly associated with anchoring a
tree?
A. Producing chlorophyll
B. Providing mechanical stability
C. Producing flowers
D. Increasing transpiration
