Several processes, such as photosynthesis and water and nutrient uptake, are simultaneously running in plants. Fluxes of processed products, such as sugars, water and nutrient ions connect the processes with each other. Highly specialised structures have developed in evolution for each process and transport phenomenon. According to the basic idea 7 of the cover theory (Chap. 2), these structures are effective, and basic idea 9 says that the biochemical regulation systems play an important role in the formation of the structures. The water transport within trees generates regularities in the structure of woody components.