Which layer of a tree contributes to its thickness by forming new cells?

The cambium is a critical layer of a tree responsible for its growth in thickness. It is a thin layer of actively dividing cells located between the xylem (wood) and phloem (bark). This layer generates new cells during the growing season, contributing to the production of both xylem and phloem. The new xylem produced contributes to the tree's mass and strength, while the new phloem is essential for the transport of nutrients and sugars produced by the leaves.

As trees age and grow, the cambial layer continuously produces new layers of xylem, which contribute to the overall increase in diameter, resulting in the formation of annual growth rings that indicate the tree's age. This dynamic capability of the cambium is crucial for a tree's adaptation to its environment, allowing it to grow and withstand various stresses.

The other options represent different parts of a tree: sapwood is the outer, active part of the xylem that conducts water and nutrients; heartwood is the older, non-living center of the tree that provides structural support; and phloem is the layer responsible for transporting sugars but does not contribute to thickness. Each of these layers plays a role in the overall function and health