ISA Tree Biology and Physiology 2 — Questions and Answers
Question 1: What is the primary function of lenticels in woody plants?
- Absorb water from the atmosphere
- Allow gas exchange through the bark (Correct answer)
- Store starch reserves
- Protect against pathogen entry
Correct answer: Allow gas exchange through the bark
Lenticels are porous areas in the bark that allow oxygen and carbon dioxide to diffuse between the atmosphere and the living cells beneath.
Question 2: During which phase of cambial activity does the cambium produce xylem cells toward the inside of the stem?
- Quiescence
- Reactivation
- Active growth (Correct answer)
- Dormancy
Correct answer: Active growth
During the active growth phase, the vascular cambium divides to produce secondary xylem (wood) toward the pith and secondary phloem toward the bark.
Question 3: What term describes the gradual death and browning of leaf tissue starting at the margins or tips?
- Chlorosis
- Necrosis
- Scorch (Correct answer)
- Anthracnose
Correct answer: Scorch
Scorch refers to browning of leaf margins and tips often caused by drought, salt damage, or vascular disruption preventing adequate water delivery.
Question 4: Which of the following best describes 'reaction wood' in angiosperms?
- Heartwood formed under stress
- Tension wood formed on the upper side of leaning stems (Correct answer)
- Compression wood formed on the lower side of branches
- Juvenile wood near the pith
Correct answer: Tension wood formed on the upper side of leaning stems
Angiosperms produce tension wood on the upper side of leaning stems or branches to pull them back toward vertical, unlike gymnosperms which form compression wood on the lower side.
Question 5: What is the role of abscisic acid (ABA) in trees under drought stress?
- Stimulates stomatal opening to increase CO2 uptake
- Promotes root elongation to reach deeper water
- Triggers stomatal closure to reduce water loss (Correct answer)
- Accelerates photosynthesis in remaining leaves
Correct answer: Triggers stomatal closure to reduce water loss
ABA is produced in roots and leaves under drought stress and signals guard cells to close stomata, reducing transpiration and conserving water.
Question 6: In tree anatomy, what is the function of the rays?
- Conduct water from roots to leaves
- Transport photosynthates radially across the stem (Correct answer)
- Anchor the tree against wind loads
- Store nitrogen for spring growth
Correct answer: Transport photosynthates radially across the stem
Rays are radially oriented bands of parenchyma cells that transport water, nutrients, and photosynthates laterally across the wood and store carbohydrates.
Question 7: What process allows trees to adjust their physiology to function optimally across a range of temperatures over days to weeks?
- Vernalization
- Acclimation (Correct answer)
- Stratification
- Phenological shift
Correct answer: Acclimation
Acclimation (also called hardening) is the reversible physiological adjustment that allows trees to function across changing temperatures over a period of days to weeks.
ISA Tree Biology and Physiology 2
What is the primary function of lenticels in woody plants?