Organ positioning, or phyllotaxis, is characterized by the divergence angles between the leaves, the most common angle being 137.5°, the golden angle. To understand the mechanistic basis of this regularity, we have used pharmacological approaches, micromanipulation, genetics, mechanics and computational modeling. At the heart of the system is a positive feedback loop between the plant hormone auxin and its transporter, the PIN1 protein. The challenge will be to construct a biologically plausible 3-dimensional computational model implemented on a realistically growing cellular template.
For reviews, see Kuhlemeier 2007 (Trends in Plant Science), 2017 (Current Biology)