Certified Arborist Practice Test

The tree structure that is primarily responsible for transporting water and minerals from the roots to the leaves is the xylem. Xylem tissue consists of specialized cells that form vessels and tracheids, allowing for the efficient movement of water through a process known as transpiration. This upward movement occurs as water evaporates from the leaves, creating a negative pressure that draws more water up from the roots through the xylem.

While the phloem also plays a crucial role in the tree's vascular system, its primary function is to transport sugars and organic nutrients produced during photosynthesis from the leaves to other parts of the tree. The cambium is a layer of merit that produces new xylem and phloem cells, helping to increase the tree's girth as it grows. Bark, the outer protective layer of the tree, does not play a direct role in the transportation of water and minerals but instead serves to protect the inner tissues from environmental damage.