What layer of a tree is primarily involved in growth?

The cambium layer is crucial for a tree's growth, as it is a thin layer of actively dividing cells located between the xylem and phloem. This layer is responsible for producing new xylem and phloem cells, which contribute to the tree's overall diameter increase over time. As the cambium cells divide, they generate secondary xylem (wood) on the inside and secondary phloem on the outside. This process not only allows for the tree's expansion in girth but also plays a vital role in the tree's ability to transport nutrients and water efficiently through the phloem and xylem.

In contrast, the xylem primarily serves to transport water and minerals from the roots to the leaves, while also providing structural support. The phloem is responsible for transporting sugars and other organic compounds produced during photosynthesis from the leaves to other parts of the tree. Heartwood, found at the core of older trees, provides stability and strength but does not participate in the growth process as it is made up of non-living cells. Understanding the function of the cambium is essential for grasping the mechanisms behind a tree's growth and development.