Symmetry-Breaking in Plant Stems

TL;DR

This paper presents a simplified auxin dynamics model explaining various plant stem morphogenesis phenomena, including phyllotaxis patterns and branch chirality, by varying a single diffusion parameter.

Contribution

It introduces a novel model linking auxin diffusion to diverse plant stem morphogenesis patterns and their dynamic changes over growth seasons.

Findings

Model reproduces random, distichous, and spiral phyllotaxis patterns.

Explains how spiral phyllotaxis can produce branches with same or opposite chirality.

Shows transition from discordant to concordant relationships during growth.

Abstract

The purpose of this paper is to present a model of a phenomenon of plant stem morphogenesis observed by Cesar Gomez-Campo in 1970. We consider a simplified model of auxin dynamics in plant stems, showing that, after creation of the original primordium, it can represent random, distichous and spiral phyllotaxis (leaf arrangement) just by varying one parameter, the rate of diffusion. The same analysis extends to the $n$-jugate case where $n$ primordia are initiated at each plastochrone. Having validated the model, we consider how it can give rise to the Gomez-Campo phenomenon, showing how a stem with spiral phyllotaxis can produce branches of the same or opposite chirality. And finally, how the relationship can change from discordant to concordant over the course of a growing season.