What does the term "inner bark" refer to?

The term "inner bark" refers to the layers of secondary phloem found within the bark of a tree. Specifically, it is the part of the bark that lies just beneath the protective outer bark layer. The secondary phloem is responsible for transporting nutrients, particularly sugars produced through photosynthesis, from the leaves to other parts of the plant, including the roots and developing tissues.

This distinction is important because it emphasizes the functional role of the inner bark in the tree's physiology. Although the cortex is included in the broader definition of bark, the inner bark specifically denotes the living part that is actively involved in nutrient conduction. In contrast, the other choices focus on different plant structures and functions that are not directly related to the concept of inner bark. Thus, understanding the role of the secondary phloem helps in appreciating how trees and other vascular plants transport essential nutrients throughout their structure.