Noisy circumnutations facilitate self-organized shade avoidance in sunflowers

TL;DR

This study demonstrates that noisy circumnutations in sunflowers act as functional noise, enhancing self-organization and shade avoidance by enabling plants to explore configurations efficiently, leading to optimized growth patterns.

Contribution

It introduces the first quantitative analysis of noisy circumnutations as a functional mechanism in plant self-organization and develops a model capturing their role in shade avoidance.

Findings

Circumnutations follow a broad velocity distribution covering three orders of magnitude.

Noisy movements facilitate exploration, leading to optimized plant arrangements with minimal shading.

The model successfully replicates observed plant dynamics and interactions.

Abstract

Circumnutations are widespread in plants and typically associated with exploratory movements, however a quantitative understanding of their role remains elusive. In this study we report, for the first time, the role of noisy circumnutations in facilitating an optimal growth pattern within a crowded group of mutually shading plants. We revisit the problem of self-organization observed for sunflowers, mediated by shade response interactions. Our analysis reveals that circumnutation movements conform to a bounded random walk characterized by a remarkably broad distribution of velocities, covering three orders of magnitude. In motile animal systems such wide distributions of movement velocities are frequently identified with enhancement of behavioral processes, suggesting that circumnutations may serve as a source of functional noise. To test our hypothesis, we developed a parsimonious model of interacting growing disks, informed by experiments, successfully capturing the characteristic dynamics of individual and multiple interacting plants. Employing our simulation framework we examine the role of circumnutations in the system, and find that the observed breadth of the velocity distribution confers advantageous effects by facilitating exploration of potential configurations, leading to an optimized arrangement with minimal shading. These findings represent the first report of functional noise in plant movements, and establishes a theoretical foundation for investigating how plants navigate their environment by employing computational processes such as task-oriented processes, optimization, and active sensing.