# Curving to fly: Synthetic adaptation unveils optimal flight performance of whirling fruits

## TL;DR

This study combines theoretical modeling and experiments with synthetic fruits to identify the optimal sepal fold angle that maximizes flight time, revealing how seed wing curvature enhances wind dispersal efficiency.

## Contribution

It introduces a bio-mimetic model and experimental validation to determine the optimal sepal curvature for seed dispersal, linking shape to flight performance.

## Key findings

- Optimal sepal fold angle maximizes flight duration.
- Synthetic experiments confirm theoretical predictions.
- Wild whirling fruits exhibit similar sepal angles.

## Abstract

Appendages of seeds, fruits and other diaspores (dispersal units) are essential for their wind dispersal, as they act as wings and enable them to fly. Whirling fruits generate an auto-gyrating motion from their sepals, a leaf like structure, which curve upwards and outwards, creating a lift force that counteracts gravitational force. The link of the fruit's sepal shape to flight performance, however, is as yet unknown. We develop a theoretical model and perform experiments for double-winged bio-mimetic 3D-printed fruits, where we assume that the plant has a limited amount of energy that it can convert into a mass to build sepals and, additionally, allow them to curve. Both hydrodynamic theory and experiments involving synthetic, double-winged fruits show that to produce a maximal flight time there is an optimal fold angle for the desiccated sepals. A similar sepal fold angle is found for a wide range of whirling fruits collected in the wild, highlighting that wing curvature can aid as an efficient mechanism for wind dispersal of seeds and may improve the fitness of their producers in the context of an ecological strategy.