My reasoning being, when you make a cut on a plant, it creates a vacuum, drawing air up into the cut. As I'm sure 99% of you know, cannabis is hollow in the very center. Different types (indica or sativa) and strains grow differently with a different dilation or space in the center or the stem. This also has to do with the amount of transpiration the plant is going through. I've noticed hydro plants are generally ALWAYS "more hollow" in the center because of their environment. They tend to transpire more fluid through their leaves which creates a need for more fluid to travel up the stem, which in turn creates a need for a larger passageway for fluids. Which I believe is an underlying factor as to why hydro gardens are "more effective producers" than soil. The ability to absorb, use and transpire water and nutrients more effectively.
and thanks for the great rating, I'm very happy I could help.