Clothing that adapts to one's needs and senses the external habitat. A lunar lava tunnel that uses bacteria, plants and fungi to create sustainable human habitats within otherwise unlivable places. Buildings grown from living things.
Such inventions may define the future, as Cornell scientists work towards engineering plants and other organisms to grow into biodegradable usable forms. But first, they need to understand the basics of how cell walls control plant growth.
A new study that uses the model plant Arabidopsis thaliana takes an important early step in this direction. Bridging the fields of plant biology and mechanical engineering, the study investigated the mechanical properties of cell walls, such as how they stretch and rebound, elongate without returning to form, and thin out when stretched. The paper was published Aug. 14 in Nature Communications.
"By understanding cell wall mechanics related to plant development, we may one day engineer plants to grow materials with desired shape and size, such as biodegradable package materials formed directly by the plant itself," said Si Chen, an Engineered Living Materials Institute (ELMI) Postdoctoral Fellow, and the paper's first author. The interdisciplinary ELMI, which launched three years ago and includes biologists, engineers and architects, aims to research and develop new functional and sustainable materials from plants, and other living organisms, such as fungi and bacteria.
When plants grow, their primary cell walls, which form the plant cell's outer layer, are involved in growth, while secondary cell walls make the structures hard once growth has ceased. This study focused on the growing stage and properties of primary cell walls.
Chen innovated experimental designs to collect data on how much force it takes to stretch the walls, and how much thinner the walls become when elongated.
"If we can engineer plants to change their form during their growth phase before it lays down the secondary cell wall, we could form something that's hard with structure based on the outer layer," said Adrienne Roeder, professor in the School of Integrative Plant Science Plant Biology Section and the Weill Institute for Cell Biology in the College of Agriculture and Life Sciences and a senior author of the study.
Chen also investigated the plant's developmental timeframe, to understand how mechanical properties change when leaves are growing fast versus when they slow down and stop growing. And she tested cell wall mechanical properties in a mutant Arabidopsis, called spiral 2, which twists as it grows, so she could evaluate the properties of how cell wall material is laid down as it spirals.
She also made a simple model to help her further discern mechanical behaviors, using five beams, representing cellulose fibers, connected in a four-sided diamond shape with a cross beam to conceptualize cell-wall architecture. Using this model, she showed how the beam behaviors (bending, reorienting, stretching, slipping) and how the connectors between these beams contribute to the overall mechanical response.
"It's the connections between these beams that are really critical," Roeder said. "It points us towards really focusing on those connector points when we engineer materials in the future."
The study's senior co-author is Meredith Silberstein, professor in the Sibley School of Mechanical and Aerospace Engineering at Cornell Engineering and founder and director of ELMI, while Roeder serves as associate director. Co-authors include Isabella Burda, Ph.D. '25 (ELMI and Weill Institute); Purvil Jani, M.S. '20, Ph.D. '25 (School of Chemical and Biomolecular Engineering); and Bex Pendrak '22 (ELMI and mechanical and aerospace engineering).
The study was funded by ELMI, the National Institutes of Health, the National Science Foundation and Chen's Sam and Nancy Fleming Postdoctoral Fellowship.
