Certified Arborist Test Tree Biology and Structure 1 — Questions and Answers
Question 1: Which tissue is responsible for transporting water and dissolved minerals from the roots upward through a tree?
- Phloem
- Xylem (Correct answer)
- Cortex
- Pith
Correct answer: Xylem
Xylem is the vascular tissue that conducts water and dissolved minerals (sap) upward from the roots to the leaves. Phloem, by contrast, transports photosynthate (sugars) downward from the leaves.
Question 2: What term describes the dead, darkened wood at the center of a tree trunk that no longer conducts water but provides structural support?
- Sapwood
- Heartwood (Correct answer)
- Cambium
- Phelloderm
Correct answer: Heartwood
Heartwood is the central column of older, non-conducting xylem. Its cells are dead and often impregnated with extractives that darken it, but it provides the tree's primary structural rigidity.
Question 3: Which of the following correctly describes the role of lenticels on a tree's bark?
- They anchor the root system to soil particles
- They produce the waxy cuticle on leaf surfaces
- They allow gas exchange between internal tissues and the atmosphere (Correct answer)
- They synthesize chlorophyll for bark photosynthesis
Correct answer: They allow gas exchange between internal tissues and the atmosphere
Lenticels are small pores in the bark that permit oxygen to diffuse into living cells and carbon dioxide to escape, performing a function analogous to stomata in leaves.
Question 4: In tree anatomy, what is the primary purpose of root hairs?
- Storing starch reserves for winter dormancy
- Greatly increasing the surface area for water and nutrient absorption (Correct answer)
- Anchoring the tree against wind throw
- Producing root exudates that suppress competing vegetation
Correct answer: Greatly increasing the surface area for water and nutrient absorption
Root hairs are thin-walled extensions of epidermal cells near root tips. Their enormous combined surface area maximizes contact with soil moisture and dissolved minerals, dramatically improving absorption efficiency.
Question 5: What name is given to the protective boundary zone a tree forms between healthy tissue and a wound or decayed area?
- Callus ridge
- Woundwood collar
- Reaction zone (Correct answer)
- Compartmentalization wall
Correct answer: Reaction zone
A reaction zone (also called a barrier zone in CODIT) is chemically and structurally altered wood that the tree produces to resist the spread of decay. It forms behind the wound and represents the most important of the four walls in compartmentalization.
Question 6: Which of the following best describes the function of the phloem in a woody tree?
- Producing new xylem and phloem cells through cell division
- Transporting photosynthetically produced sugars from leaves to other parts of the tree (Correct answer)
- Providing the rigid cellulose framework of the cell wall
- Absorbing atmospheric nitrogen for protein synthesis
Correct answer: Transporting photosynthetically produced sugars from leaves to other parts of the tree
Phloem conducts dissolved organic compounds — primarily sucrose produced in the leaves — downward and outward to growing tissues, roots, and storage organs. This flow is called translocation.
