Which layer of a tree trunk is responsible for growth?

The cambium layer of a tree trunk plays a critical role in the growth of the tree. It is a thin layer of actively dividing cells located just beneath the bark. This layer produces new phloem cells, which transport nutrients and sugars produced by photosynthesis, and new xylem cells, which facilitate water and nutrient uptake from the roots. As the cambium generates more xylem and phloem over time, it allows the tree to increase in diameter, contributing to the overall growth of the trunk.

The sapwood layer is primarily responsible for conducting water and nutrients from the roots to the leaves, but it does not generate new growth. Heartwood functions as a supportive center and does not participate in growth; instead, it provides structural stability and may contain natural preservatives that help the tree resist decay. The pith, located at the very center of the tree, serves as a store for nutrients and may also help with transport during the early stages of growth in younger trees, but it does not contribute significantly to the growth of mature trees. Thus, the cambium is the layer precisely responsible for the growth of the tree itself.