Image credit: Madeleine Seale
Abstract
Animal migration is highly sensitised to environmental and biological cues, yet plant dispersal is considered largely passive. The common dandelion, Taraxacum officinale, is a classic example of a wind-dispersed plant and has an intricate haired pappus facilitating flight. This pappus facilitates enables the formation of a separated vortex ring (SVR) during flight; however, the pappus structure is not static but reversibly changes shape by closing in response to moisture. Here we characterise the biomechanical function of the pappus morphing regarding SVR dynamics and flight capacity. When the pappus closes, the falling velocity is greatly increased and the velocity deficit within the vortex decreased. To understand the implications of this structural-functional change, we used historic meteorological data to simulate dispersal distance. Dispersal distances were reduced with the pappus closed, and so was detachment. We propose that moisture-dependent pappus-morphing serves to retain seeds in favourable moist niches, providing a form of informed dispersal that has not been characterised in plants on such a short-term, responsive time scale.
