Roses, long admired for their beauty and symbolic richness, owe their iconic petal shape to a mechanical process that has remained largely mysterious—until now. According to a new study, the pointed cusps that gradually form at the edge of rose petals as they grow are shaped not by the well-known mechanics behind wavy leaves, but by a distinct geometric frustration called Mainardi-Codazzi-Peterson (MCP) incompatibility. According to the findings, this stress-focusing phenomenon not only sculpts the rose’s form but also feeds back to influence how the petal grows, offering new insights into the mechanics of nature, and potential inspiration for the design of bio-inspired materials. The intricate curves and curls of leaves and flower petals often arise from the interplay between natural growth and geometry. In elastic materials, like plant tissues, growth can create a mismatch between the material’s natural geometric preference and what is physically possible, resulting in inherent stresses known as geometric incompatibilities. As these stresses accumulate, they can result in shape changes – an effect known as Gauss incompatibility. This explains features like the rippling edges of leaves and petals. However, the distinctive, sharply pointed cusps along the edges of rose petals stand apart from the soft, wavy patterns seen in many other flowers – features that cannot be explained by traditional Gauss incompatibility.

 

Here, Yafei Zhang and colleagues combined theoretical analysis, computational modeling, and experimental fabrication of synthetic disc petals to investigate growth-induced mechanical instabilities in rose petals. Zhang et al. discovered that the unique shapes of rose petals are not governed by Gauss incompatibility, but instead by a unique type of geometric frustration known as Mainardi-Codazzi-Peterson (MCP) incompatibility. Unlike traditional shape changes driven by Gauss-type mismatches, this mechanism concentrates stress in highly localized areas, giving rise to the sharply defined cusps seen in roses. Moreover, the authors show that the intense concentration of stress at petal cusps influences how the surrounding tissue grows and takes shape, revealing a powerful feedback loop between biological growth, geometric constraints, and mechanical forces. “Identifying Mainardi-Codazzi-Peterson incompatibility as a shaping mechanism is not only an important milestone in morphogenesis research but also an inspiration for new designs of shape-morphing materials and structures,” write Qinghao Cui and Lishuai Jin in a related Perspective. “Combining Gauss and Minardi-Codazzi-Peterson incompatibilities could give rise to deformation behaviors that have yet to be seen.”

A new approach to drug design can deliver medicine directly to the gut in mice at significantly lower doses than current inflammatory bowel disease treatments.

The proof-of-concept study, published today in Science, introduced a mechanism called ‘GlycoCaging’ that releases medicine exclusively to the lower gut at doses up to 10 times lower than current therapies.

“With this technique, we have the ability to deliver not just steroids, but a range of drugs including anti-microbial compounds directly to the gut, potentially helping people with inflammatory bowel disease, gut infections and more,” said co-senior author Dr. Harry Brumer, a professor in the UBC department of chemistry and Michael Smith Laboratories (MSL).

More than 1,200 physicists from around the world will convene to present new research at the 56th Annual Meeting of the American Physical Society’s Division of Atomic, Molecular and Optical Physics. The conference will be held in person only at the Oregon Convention Center in Portland, Oregon June 16-20.

UCLA and UCSD scientists inserted DNA-encoding methylmercury detoxification enzymes into the genome of an abundant human gut bacterium. The engineered bacterium detoxified methylmercury in the gut of mice and dramatically reduced the amount that reached other tissues, such as the brain and liver. Mice given an oral probiotic containing the engineered microbe and fed a diet high in bluefin tuna had much lower methylmercury levels than expected, suggesting that a probiotic might eventually make it safer for people to consume fish. Researchers performed the tests using pregnant mice and found lower levels of methylmercury in both maternal and fetal tissues, and lower signs of mercury toxicity in the fetal brain.