Moisture‐Dependent Morphing Tunes the Dispersal of Dandelion Diaspores

Abstract

Long distance dispersal (LDD) is considered particularly important for plant range expansion. Such events are rare, however, and for wind-dispersed species updrafts or extreme weather events are required. Despite the importance of LDD for plant population dynamics, dispersing long distances is risky to the survival of individual seeds and the majority of seeds disperse short distances. The extent to which most wind dispersed plants can manipulate dispersal ranges of individual seeds is debatable as wind speeds are generally more variable than seed traits. Here, we present a dynamic mechanism by which dandelion (Taraxacum officinale) seeds can regulate their dispersal in response to environmental conditions. We used time lapse imaging to observe shape changes in dandelion pappi. We also analysed diaspore fluid mechanics in two wind tunnels and used particle image velocimetry (PIV) to understand flight characteristics of the morphing structure. We have found that by changing the shape of the pappus when wet, detachment from the parent plant is greatly reduced and seed falling velocities are increased with a significant change in velocity deficit behind the seed. We suggest that this may be a form of informed dispersal maintaining LDD in dry conditions, while spatiotemporally directing short-range dispersal toward beneficial wetter environments.

Keywords: wind dispersal, biological fluid mechanics, abscission bias, dandelion, Asteraceae