The Constraints of Global Form on Phyllotactic Organization: the Case ofSymplocarpus(Araceae)

The present paper describes a formal analysis of the constraints imposed by a change of global form on the phyllotactic organization in the inflorescence ofSymplocarpus. By combining a dynamic model of phyllotaxis with a general model of allometric growth, we show that as the length-to-width ratio of the inflorescence increases, then the number of parastichies decreases while the plastochrone ratio increases. Subsequent observations prove that these theoretical conclusions emerging from the analysis of the global form ofSymplocarpusare exact. Our analysis offers experimentalists the possibility of verifying the existence of particular allometric relationships in the different phases of development ofSymplocarpusand related species.