This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Roses are known for their thorns, the sharp structures that can sting and prickle the skin. Thorns, botanically known as prickles, are thought to discourage animals from feeding on plants and may also help climbing roses grip other vegetation.
Compared with the prickles found on many other plants and those artificially created by humans, rose thorns have a somewhat unusual shape. When sliced across their width, various other stingers are approximately round, yet rose prickles tend to have an oval cross section. Researchers at Technical University of Denmark and Aarhus University recently tried to better understand why roses may have evolved this unusually flat thorn geometry by running laboratory experiments with artificial prickles and skin-like materials.
Their findings, published in Journal of the Royal Society Interface, suggest that the oval shape of rose prickles could be a compromise between more stable round stingers and flattened, less stable prickles that look more like tiny blades. "I have worked on stinging and cutting physics for a few years now, drawing inspiration from the book 'On Size and Life' by McMahon and Bonner, published in 1983," Kaare H. Jensen, senior author of the paper, told Phys.org.
"It is an older book, but it has nice examples of how physics could be involved in limiting the functionality of both technical and living systems. In particular, the analyses of steel nail length-diameter relations and the scaling of rowing speed with number of oarsmen are very elegant. We simply tried to understand why rose prickles have an oval cross section." When studying various stingers (i.e., sharp and pointed structures) found in nature, Jensen realized that rose prickles differed from those of many other plants.
Specifically, he found that they had an unusually flattened oval cross section, particularly when compared with the cylindrical spines of other plants such as cacti or hawthorn trees. "Circular beams, such as a nail or a needle, are good for poking," said Jensen. "So, if the idea is to simply protect the plant, I don't see a reason not to have circular stingers.
This surprised me." To understand why rose prickles are flatter than those of many other plants, the researchers created artificial stingers using a flexible silicone-based material called polydimethylsiloxane (PDMS). They ensured that these stingers differed in their cross-sectional shapes, ranging from approximately circular to increasingly narrow and flatter shapes. They then moved the artificial stingers through gelatin using a small robot.
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