Material Composition Gradient Controls the Autonomous Opening of Banksia Seed Pods in Fire-Prone Habitats

Friedrich Reppe, Lorenzo Guiducci, Rivka Elbaum, Peter Werner, John W.C. Dunlop, David J. Merritt, Peter Fratzl, Michaela Eder

Research output: Contribution to journalArticlepeer-review

Abstract

Plants possess intriguing mechanisms to cope with environmental stresses and disturbances, and respond to stimuli due to their sessile nature. Banksia attenuata, a tree or shrub species native to southwestern Australia, integrates numerous traits to persist and regenerate through reoccurring bushfires. A key trait of Banksia is that of serotiny: Plants can retain seeds for many years within the canopy protected inside durable seed pods (follicles), with seed release commonly triggered by the heat of bushfire, and subsequent rainfall. Here, we show that the tissue of the two follicle valves is arranged in layers, which not only counteract as a hygroscopic bi-layer, but prevent delamination as their opposed physical properties converge toward the interface. Moreover, a shape-memory effect of the active layer stores energy after the first opening step for the second opening step, ensuring delayed seed release only after the fire is extinguished. Detailed experiments reveal how structure, composition and physical properties of the tissue layers facilitate first longevity and later the complex autonomous seed release. Based on these findings, two numerical models illustrate the mechanics of the layers more deeply. These results highlight the importance of graded material properties for the function of natural actuators.

Original languageEnglish
JournalAdvanced Functional Materials
DOIs
StateAccepted/In press - 2025

Keywords

  • banksia
  • bi-layer
  • energy
  • seed release
  • serotiny
  • shape-memory
  • wood fibers

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • General Chemistry
  • Biomaterials
  • General Materials Science
  • Condensed Matter Physics
  • Electrochemistry

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