Surface tension propulsion of fungal spores

Xavier Nobliri, Sylvia Yang, Jacques Dumais

Research output: Contribution to journalArticlepeer-review

57 Scopus citations

Abstract

Most basidiomycete fungi actively eject their spores. The process begins with the condensation of a water droplet at the base of the spore. The fusion of the droplet onto the spore creates a momentum that propels the spore forward. The use of surface tension for spore ejection offers a new paradigm to perform work at small length scales. However, this mechanism of force generation remains poorly understood. To elucidate how fungal spores make effective use of surface tension, we performed a detailed mechanical analysis of the three stages of spore ejection: the transfer of energy from the drop to the spore, the work of fracture required to release the spore from its supporting structure and the kinetic energy of the spore after ejection. High-speed video imaging of spore ejection in Auricularia auricula and Sporobolomyces yeasts revealed that drop coalescence takes place over a short distance (∼5 μm) and energy transfer is completed in less than 4u.s. Based on these observations, we developed an explicit relation for the conversion of surface energy into kinetic energy during the coalescence process. The relation was validated with a simple artificial system and shown to predict the initial spore velocity accurately (predicted velocity: 1.2 ms-1; observed velocity: 0.8ms-1 for A. auricula). Using calibrated microcantilevers, we also demonstrate that the work required to detach the spore from the supporting sterigma represents only a small fraction of the total energy available for spore ejection. Finally, our observations of this unique discharge mechanism reveal a surprising similarity with the mechanics of jumping in animals.

Original languageEnglish
Pages (from-to)2835-2843
Number of pages9
JournalJournal of Experimental Biology
Volume212
Issue number17
DOIs
StatePublished - 2009

Keywords

  • Aurlcularia auricula
  • Ballistospores
  • Spore dispersal
  • Surface tension
  • Wetting phenomena

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