Certified Arborist Test 2025 – 400 Free Practice Questions to Pass the Exam

The cambium is a vital layer of tissue in a tree that plays a crucial role in the plant's growth. It is responsible for the production of new cells that contribute to the increase in trunk and branch thickness, a process known as secondary growth. This layer is located between the bark and the wood (xylem) of the tree, and it generates new layers of xylem towards the inside and phloem towards the outside, effectively enhancing the diameter of the tree over time.

While the cambium does facilitate some of the processes associated with nutrient and water transport, its primary and distinctive role centers around promoting the tree's growth in thickness. Additionally, although trees do store energy, that function is mainly carried out by other tissues such as parenchyma cells in the xylem rather than by the cambium itself. Thus, the main function of cambium is accurately identified as facilitating growth in thickness.