With regard to compartmentalization in woody plants, Dr Alex Shigo discovered that trees deal with injury and decay by erecting physical and chemical barriers that serve to 'wall off' the injury/decay from healthy tissue. You can learn more by using the searchwords Shigo CODIT, 'CODIT' being an acronym for 'compartmentalization of decay in trees).
When it comes to direct relationships between specific roots and branches, how strict that relationship is varies significantly by species. Woody plants like junipers and yews have a relationship between roots and branches that is so strict, when a root or branch dies, it's counterpart also dies. There are yews in the UK so old and large that the the entire trunk has rotted away, leaving a circle of vertical living veins connected directly to a single branch, which then divides into higher orders of branches. IOW, the branch served by a single root divides into secondary, tertiary, quaternary ..... branches, but the root is connected to a live vein which connects to the base of a primary branch. Thuja occidentalis also has the same direct root to branch connection such that an injured root or branch affects the counterpart it's connected to.
In other trees, the connection is less direct, meaning that destruction of or damage to a root has a widely varying degree of impact on branches and destruction of or damage to branch has a widely varying impact on roots. In some tree species the movement of water, nutrients, and photosynthate can readily move diagonally, such that damage to a branch or root doesn't have a significant effect on it's opposite end counterpart. In trees where water/sap flow moves diagonally with facility, the closer the damaged root or branch is to a branch or root vertically aligned with its counterpart, the more likely one is to be affected by the other. IOW, a branch 2 ft directly above a damaged root is much more likely to be killed or affected by the demise of its counterpart than if the branch was 10 ft directly above the damaged root.
Al
