Tree structure forms the physical framework for metabolic processes and transport of substances to take place. It also forms the means for the tree to reach towards resources provided by its environment. On the other hand, the growth process continuously creates new structures. Thus structure, processes and transport are strongly interconnected, and the efficiency of whole-tree functioning in terms of energy and raw material use is dependent on how well these components are balanced with each other. For example, crown structure influences light interception and thus the photosynthetic production of the foliage. The cross-sectional area of the water conducting wood, its permeability and its length all have a significant role in controlling water and assimilate transport in trees. The spatial distribution of fine roots determines how trees access nutrients and water. Understanding and modelling tree growth largely relies upon how well we understand these interconnections.
Imbalance would be wasteful with respect to both energy and raw material, therefore balanced connections between structure, processes and transport have been subject to strong selective pressures. As a result, efficient and balanced structures adapted to different environments have emerged in the course of evolution of organisms. Optimisation models incorporating the interplay between structure and function can be efficient tools for understanding plant form and resource allocation.