Oval cross-section of rose prickles may balance stability and cutting efficiency
Researchers from the Technical University of Denmark and Aarhus University tested artificial prickles on skin-like materials to understand why rose thorns have an oval cross-section. Their findings, published in Journal of the Royal Society Interface, suggest this shape is a compromise between more stable round stingers and flattened, blade-like prickles. The work draws on principles from the book 'On Size and Life' to explore physical constraints on living systems.
The research team fabricated artificial prickles from polydimethylsiloxane, a flexible silicone, varying their cross-sectional geometry from circular to increasingly flattened. A small robot moved these test structures through gelatin, which served as a skin-like proxy, allowing the scientists to measure how each shape performed under realistic shearing forces.
The experiments revealed that circular stingers tended to bend or buckle when subjected to lateral movement, while oval-shaped prickles maintained better cutting performance. This mechanical advantage may explain why roses evolved this distinctive geometry, potentially aiding the plant in both defense and climbing support. The work draws conceptual inspiration from the 1983 book "On Size and Life," which explores how physical constraints shape biological systems.
This research could inform biomimetic design in fields ranging from medical device manufacturing to agricultural engineering, where understanding how shape affects cutting efficiency matters. Gardeners and botanists may gain practical insight into why certain plants are more irritating to handle. The findings also demonstrate how evolutionary biology and physics intersect, potentially encouraging interdisciplinary approaches in university curricula and inspiring future studies on how other plant structures are optimized for multiple competing functions.