The research team found that miscanthus and sorghum — both C₄ plant species — occupy a distinct niche of the leaf economics spectrum (LES), with greater photosynthetic rates and nitrogen use efficiency than more common C₃ plants.

The study, published in Plant, Cell & Environment, was led by Postdoctoral Researcher Shuai Li of CABBI, a U.S. Department of Energy-funded Bioenergy Research Center. Li works with Lisa Ainsworth, a Plant Physiologist with the U.S. Department of Agriculture’s Agricultural Research Service (USDA-ARS) Global Change and Photosynthesis Research Unit and Adjunct Professor of Plant Biology and the Carl R. Woese Institute of Genomic Biology (IGB) at the University of Illinois Urbana-Champaign.

LES describes relationships among leaf traits reflecting fundamental trade-offs underpinning key ecological strategies for resource acquisition and use in plants. It is largely based on information from C₃ species in natural environments and has been studied rarely in C₄ crops, which use a different carbon-fixation process: C₄ plants convert sunlight energy into 4-carbon molecules, whereas the first photosynthesis product of C₃ plants is a 3-carbon molecule. C₄ plants make up about 3% of land plant species but include major sources of food and biofuels worldwide, such as maize, sorghum, and miscanthus.

The CABBI researchers showed that C₄ bioenergy crops occupy a distinct range of the LES, with higher photosynthetic rates and greater nitrogen use efficiency. Additionally, Miscanthus × giganteus genotypes with different ploidy levels (or number of chromosome pairs) exhibit leaf trait divergence and distinct leaf functional relationships compared to C₃ plants.

By expanding the trait relationships described in the LES to include C₄ crops in agricultural conditions, the study enhances understanding of overall worldwide patterns in leaf functional relationships and offers insight into the potential for ploidy to improve resource use efficiency, Ainsworth said.

“This study took advantage of diverse plantings of miscanthus in Illinois and Mississippi to test how leaf properties vary in different lines and in different environments,” Ainsworth said. “We studied the investment that different miscanthus lines make in leaf structure and nutrient content — information that is crucial for modeling productivity of bioenergy crops and where they can be grown.”

CABBI co-authors on the study included University of Illinois Crop Sciences and IGB Professors Erik Sacks and D.K. Lee; Andrew Leakey, CABBI Director and Professor and Head of the Department of Plant Biology, also with IGB; Professor Brian Baldwin and Assistant Research Professor Jesse Morrison from Plant and Soil Sciences at Mississippi State University; and Nicholas R. Labonte, former Postdoc with Sacks.

Other co-authors: Christopher A. Moller and Noah G. Mitchell of IGB and USDA-ARS; Duncan G. Martin of Plant Biology at Illinois; Sampurna Saikia of Crop Sciences at Illinois; and John N. Ferguson of IGB and the Department of Plant Sciences at the University of Cambridge, UK.

“Jargon is pervasive in medicine and the opportunity for misunderstanding due to this terminology begins the instant that physicians introduce themselves to patients,” said Emily Hause, MD, MPH, a pediatric rheumatology fellow at the U of M Medical School. “We found that most people can’t define specialty names nor correctly rank medical seniority titles. Physicians should describe their medical specialty and role on the patient’s care team in plain language to help reduce this source of potential confusion.”

Volunteer participants at the 2021 Minnesota State Fair completed an electronic survey that measured their knowledge of medical specialties and titles. Of the 14 specialties included in the survey, six specialties were correctly defined by less than half of the respondents:

• Neonatologists: 48%
• Pulmonologists: 43%
• Hospitalists: 31%
• Intensivists: 29%
• Internists: 21%
• Nephrologists: 20%

When asked to rank medical roles, only 12% of participants correctly placed these titles in order: medical student, intern, senior resident, fellow and attending.

Further research is suggested to survey knowledge on additional specialties and obtain more demographic information.

This research was supported by the National Institutes of Health’s National Center for Advancing Translational Sciences grant UL1TR002494. Funding was also provided by the University of Minnesota Driven to Discover grant.

Story Source:

Materials provided by University of Minnesota Medical School. Original written by Alex Smith. Note: Content may be edited for style and length.

However, it is usually very time-​consuming and costly for farmers to collect and dispose of conventional polyethylene (PE) film after use. In addition, it isn’t possible to re-​collect all of the thin PE films, as they tear easily. This means PE-​pieces remain on and in the soil and accumulate there, because PE doesn’t degrade.

Biodegradable mulch film is a promising alternative, because — in contrast to PE film — it ideally does not to leave behind any polymer components in the soil environment. The biodegradable polymers it contains are deliberately designed so that microorganisms can use them to generate energy and build cell biomass. The biodegradable polymers have intended chemical “breaking points” in their backbone structure. Naturally occurring microorganisms, such as those in soil, can release enzymes into their environment that attack these points in the polymers and break them down. The small degradation products released are then taken up by the microbes and ultimately respired to form the final product, CO₂.

That’s why proving CO₂ formation from polymer carbon is crucial for biodegradation. Also because in addition to truly biodegradable plastics, there are falsely labelled ones based on PE containing specific additives. These films break down only into very small microplastics that are no longer visible to the naked eye. And because these aren’t degraded by microorganisms, they accumulate in the environment.

New approach captures all aspects of biodegradation

Until now based on existing methods, it hasn’t been possible to follow the process of polymer biodegradation in its entirety. But over the past few years, the Environmental Chemistry Group at ETH Zurich has developed a new approach to track and measure whether and to what degree a polymer biodegrades in a soil. Their findings have just been published in NatureCommunications.

These results could change the way polymer biodegradation is studied in the future. The project also involved researchers from ETH’s Earth Sciences department and Eawag, in addition to employees from the chemical company BASF.

This new approach is based on using polymers labelled with stable carbon isotopes (¹³C). This labelling allows the researchers to selectively track the polymer’s ¹³C during biodegradation in the soil, so they can unmistakably demonstrate that biodegradation is indeed occurring. Until now, plastic biodegradability had been tested only with non-​isotopically labelled polymers. A polymer (or a plastic material consisting of one or more polymers) is certified as biodegradable if the fraction of added polymer carbon converted into CO₂ exceeds a predefined level over a specific incubation period. The standard for biodegradable mulch film, for example, requires two-​year soil incubations in which at least 90 percent of the mulch film carbon is “mineralised” into CO₂.

These test methods are well established as a suitable means for detecting polymer mineralisation. However, they do not capture the full extent of the biodegradation, as they measure only CO₂ formation. Consequently, researchers using today’s standard methods have been unable to detect the amount of polymer carbon remaining in the soil at the end of an incubation period. In addition, it was unclear whether this remaining carbon was present still in the form of the added polymer or whether microorganisms had already incorporated it into their biomass.

Closed carbon mass balances

The approach developed by the ETH researchers and their colleagues eliminates these ambiguities. In their tests, they used ¹³C-​labelled polybutylene succinate, or PBS — a commercially important biodegradable polyester that is also used in mulch films.

The researchers were now able to selectively track the ¹³C in the PBS during biodegradation: in addition to determining mineralisation to ¹³CO₂, the authors demonstrated complete mass balances for the PBS carbon by quantifying the residual amount of PBS-​derived ¹³C that remained in the soil after incubation.

“It was gratifying for us to see closed carbon mass balances over the 425 days of soil incubation. This showed that we can accurately determine where the polymer carbon ends up — about two-​thirds in CO₂ and one-​third in soil — over these very long incubation periods,” explains the study’s lead author, Taylor Nelson, who earned his doctorate in the Environmental Chemistry Group.

The researchers also wanted to know in which form the carbon added as PBS remained in the soil. How much was incorporated into the microbial biomass and how much was still present as residual PBS?

To answer this question, the authors extracted and quantified the residual PBS from the soil at the end of the incubations. They were able to show that while most of the carbon was still present as PBS, a significant amount — 7 percent — of the added PBS carbon had been incorporated into the microbial biomass.

The ability to determine exactly how much polymer remains and how much polymer carbon has been incorporated into biomass is essential for future studies and for the development of new biodegradable polymers. “We can now systematically test for soil conditions and polymer properties that allow for complete biodegradation of the polymers to CO₂ and to microbial biomass — and we can assess factors that may slow down polymer biodegradation over time,” explains Michael Sander, Professor in the ETH Environmental Chemistry Group.

This work is already underway: using the new approach, the group is currently investigating the biodegradation of further polymers in various agricultural soils, including in the field. “In this way, we want to ensure that biodegradable polymers live up to their name and don’t remain in the environment,” says Kristopher McNeill, Professor of Environmental Chemistry at ETH Zurich and head of an eponymous research subgroup.

“Replacing conventional polymers with biodegradable ones can help reduce plastic pollution, especially for applications in which polymers are used directly in the environment such that there’s a high likelihood that the polymers will remain there after use,” Sander points out.