Only a positive interaction on bHLH genes or a negative one on CPC (rows in grey) produces an increase in trichome density and maintains the spaced-out pattern. The sign of interaction is in parentheses. Asterisks indicate an interaction probability PGA< 1, while no asterisk means that this probability was equal to one. The two cases PGA= 1 and PGA< 1 are only shown when their results are different. These simulations were performed in 20 × 20 matrices with the following parameter values: DCPC= 0.05, DTRR= 0.05, DTTG= 0.03.