Curved Reaction–Diffusion Fronts Generate Quasi-Symmetric Phyllotaxis in a Chemical Turing System

Chemical systems provide controllable platforms for uncovering general principles of self-organization. Phyllotactic structures are a prominent example of natural patterns, arising when radial growth is coupled to spot formation with an intrinsic spatial wavelength. Although Turing reaction–diffusion models can generate phyllotactic patterns, this connection has not been demonstrated experimentally in an established chemical Turing system. Here we show that a propagating front in the chlorine dioxide–iodine–malonic acid reaction converts front-localized spot formation into phyllotactic organization. A planar front produces staggered, locally hexagonal rows, whereas curved fronts organize successive rows into paired, quasi-symmetric parastichy families. The experiments reveal two geometry-dependent subtypes: a radius-scaling form during radial expansion and a wavelength-preserving form during radial contraction. Expansion maintains near-half-wavelength row offsets; contraction produces more variable, frequently smaller offsets. These results establish an experimental link between chemical Turing pattern formation and phyllotaxis.