A Dynamical Phyllotaxis Model to Determine Floral Organ Number
Fig 2
Emergence of multiple whorls in model simulations.
A. Geometric assumptions of the model. B. The initiation process. A new primordium (i) is initiated at the edge of the floral meristem (FM; green circle) where the initiation potential Uini takes the minimum value. i, i −1, and i −2 are the primordium indices that denote the initiation order. Uini exponentially decreases with time (α) and the distance between primordia (λini). C. The growth process. Each primordium (k) moves at the outside of the circular FM, depending on the growth potential Ug, k. Primordium k rarely moves against the gradient (grey thin arrow), but mostly follows the gradient (black thick arrow; see the Model section). D–F. Emergence of whorled-type pattern with increasing meristem radius R0 and temporal decay rate α. Left panels: Spatial pattern after 15 primordia (red circles) initiated in an indexed order at the meristem edge (green circle; r = R0). Middle panels: Radial distance (black) from the meristem center as a function of the primordium initiation index (left panel) averaged over 400 replicate Monte Carlo simulations. Error bars represent twice the S.D. Red circles are a set of representative samples. Right panels: Time evolution of the radial coordinates of each primordium averaged over 400 replicates. Error bars show 2 S.D. The arrowheads in D and F indicate the growth arrest of the fifth and sixth primordia, respectively. Colors denote the index of the primordia. Green line in the left, middle and right panels denotes the meristem edge. (R0, α) = (20.0,0.0) in D, (5.0,0.0) in E and (20.0,2.0) in F. β = 1.0 × 104, λini = λg = 10.0, τ = 300, and σr = σθ = 0.05 in D–F.