Which part of a tree is primarily responsible for nutrient and water transport?

The sapwood is primarily responsible for nutrient and water transport within a tree. This layer, which is located just beneath the bark, contains living cells that are actively involved in the movement of water and nutrients from the roots to the rest of the tree. The sapwood's xylem tissue facilitates the upward movement of water, while the phloem transports carbohydrates and other nutrients produced during photosynthesis from the leaves to various parts of the tree.

In contrast, heartwood, which is the older, inner wood of the tree, provides structural support but is no longer involved in the transport of water and nutrients as it is composed primarily of dead cells. Bark serves as a protective outer layer and plays roles in protection and insulation, but it does not actively transport water and nutrients. Roots do play a crucial role in absorbing water and minerals from the soil, but the actual transport process to the rest of the tree occurs in the sapwood. Thus, the sapwood is the key component involved in the transport of vital resources necessary for the tree's growth and health.