Which layer of a tree is responsible for secondary growth?

The cambium layer of a tree plays a crucial role in secondary growth, which is the increase in the girth of a tree or plant. The cambium is a thin layer of meristematic cells located between the xylem (wood) and phloem (the layer that transports nutrients). It is in this layer that cell division occurs, leading to the production of new xylem cells towards the inside and new phloem cells towards the outside.

As the cambium produces new cells, it allows the tree to grow in thickness, supporting increased structural stability and nutrient transport. This is essential for trees as they age, allowing them to support greater weight and withstand environmental stresses.

While heartwood, sapwood, and phloem have important functions in a tree’s growth and sustainability, they do not contribute to secondary growth in the same way the cambium does. Heartwood comprises the dense inner part of the tree, providing stability but is no longer involved in transporting nutrients or water. Sapwood is the living outer layer of the xylem, involved in the transport of water; however, it is the cambium that is specifically responsible for the secondary growth process. Phloem serves to transport nutrients from the leaves to