AUTHOR=Horstmann Martin , Buchheit Hannah , Speck Thomas , Poppinga Simon 

TITLE=The cracking of Scots pine (Pinus sylvestris) cones

JOURNAL=Frontiers in Plant Science

VOLUME=Volume 13 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2022.982756

DOI=10.3389/fpls.2022.982756

ISSN=1664-462X

ABSTRACT=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 increasingly 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. Based on our results, we propose an interplay of humidity and temperature to be responsible for an ecologically optimized timing of (first) cone opening and seed release, in which resin works as a crucial chemical-mechanical latch system.