Noise-mediated self-organization in mutually shading sunflowers

Examples of collective behavior in biological systems are widespread; however, less attention has been given to plant systems. This is mostly due to the conceptually different type of movements in plants, classified as tropic, growing in the direction of external stimuli; or nastic, inherent movements due to internal cues such as the exploratory circumnutations. Here we study a system of mutually shading neighboring sunflowers, where interactions mediated by the shade response have been found to underpin a self-organized zig-zag growth pattern. We develop a minimal model which describes interacting sunflowers as growing repulsive disks tethered to an initial position, and interprets circumnutations as noise. Informing our model with experimental values enables us to identify the role of circumnutations as facilitating the observed self-organization.