Original video: https://youtu.be/ii1EG-wRX1E
Pine cones show functionally highly resilient, hygroscopically actuated opening and closing movements, which are repeatable and function even in millions of years old, coalified cones. Although the functional morphology and biomechanics behind the individual seed scale motions are well understood, the initial opening of the cone, which is often accompanied by an audible cracking noise, is not. We therefore investigated the initial opening events of mature fresh cones of Scots pine (Pinus sylvestris) and their subsequent motion patterns. Using high-speed and time lapse videography, 3D digital image correlation techniques, force measurements, thermographic and chemical-rheological resin analyses, we are able to draw a holistic picture of the initial opening process involving the rupture of resin seals and very fast seed scale motion in the millisecond regime. The rapid cone opening was not accompanied by immediate seed release in our experiments and, therefore, cannot be assigned to ballistochory. As the involved passive hydraulic-elastic processes in cracking are very fine-tuned, we hypothesise that they are under tight mechanical-structural control to ensure an ecologically optimised seed release upon environmental conditions suitable for wind dispersal. In this context, we propose an interplay of humidity and temperature to be the external “drivers” for the initial cone opening, in which resin works as a crucial chemical-mechanical latch system
We used high-speed video to capture the initial cracking and opening of Scots Pinecones. Our analysis of 36 opening events across six cones reveals that an average of 3.7 scales move simultaneously during each event, with up to 7 scales moving at once. This video explores the fascinating mechanics behind this natural process.
Keywords: Hygroscopy, initial opening, pinecone, plant movement, seed release
Citation: Horstmann M, Buchheit H, Speck T and Poppinga S (2022) The cracking of Scots pine (Pinus sylvestris) cones. Front. Plant Sci. 13:982756. doi: 10.3389/fpls.2022.982756
Received: 30 June 2022; Accepted: 13 September 2022;
Published: 18 October 2022.
Attribution 4.0 International — CC BY 4.0 - Creative Commons
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