The vascular cambium is a thin layer of dividing cells. What does it produce?
- Heartwood toward the inside and cork toward the outside
- Phloem toward the inside and xylem toward the outside
- Xylem toward the inside and phloem toward the outside
- Bark toward the inside and pith toward the outside
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C. Xylem toward the inside and phloem toward the outside
The cambium lays down new xylem (wood) on its inner side and new phloem (inner bark) on its outer side, which is how the trunk grows in girth. The reversed order is a common mix-up.
Reference: Arborist certification study guide: Tree Biology (meristems)
Which statement about respiration in a tree is correct?
- It takes place in all living cells, day and night
- It stops completely once the leaves have dropped
- It takes place only in green leaves during daylight
- It happens only in the roots during the growing season
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A. It takes place in all living cells, day and night
Respiration releases the energy stored in sugars and goes on in every living cell around the clock, including roots and dormant tissues. Photosynthesis, not respiration, is the process limited to green tissue in light.
Reference: Arborist certification study guide: Tree Biology (respiration)
In the CODIT model, which wall is formed by the cambium after wounding and separates wood present at the time of injury from wood formed later?
- Wall 3
- Wall 1
- Wall 2
- Wall 4
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D. Wall 4
Wall 4, the barrier zone, is laid down by the cambium after injury and is the strongest wall; it keeps decay out of wood formed afterwards. Walls 1 to 3 are in wood that already existed when the wound was made.
Reference: Shigo, CODIT model; arborist study guide: Tree Biology