by Food Research International analyzed the triple effect of climate change on soybean quality – increased carbon dioxide (CO₂), high temperatures, and drought. Using predictive modeling powered by artificial intelligence (AI) and based on experimentally verified data, the study assessed how these pressures would affect the beans. It concluded that the seeds would change their composition, producing 50% more beans but of lower nutritional quality.
The study was led by scientists from the Laboratory of Ecological Plant Physiology (LAFIECO) in the Department of Botany at the University of São Paulo's Institute of Biosciences (IB-USP) in Brazil. The scientists highlighted a 20% reduction in starch content and a 6% reduction in protein content in beans exposed to the triple impact. Furthermore, they observed a significant increase in amino acid content (175%). "That increase in amino acids was unexpected. We don't even know the effect of it on animals. We need to understand the effects of the triple impact on protein metabolism, which is very important for soybeans used in animal feed. We've seen that protein decreases in drastic climate change scenarios. Additionally, the bean loses starch, meaning less energy," summarizes Marcos Buckeridge , coordinator of LAFIECO.
The researcher states that the obtained data can help calibrate predictive models for global agriculture in the context of the impacts of climate change, as reported by the Intergovernmental Panel on Climate Change (IPCC). The group responsible for the study is composed of researchers in the fields of bioinformatics, plant physiology and biochemistry, chemistry, statistics, and mathematical modeling. They are pioneers in examining the combined effects of these stresses on soybean crops. This is the first study, however, to estimate the combined impact of all three factors, indicating what might happen to the crop.
Buckeridge points out that the fertilizing effect of increased carbon dioxide on plants is well documented in the literature. "It causes the plant to grow faster, enabling the production of more seeds. And what about when drought is also present? We discovered that CO₂ protects the plant against the effects of drought. Even a moderate drought causes the plant to produce fewer seeds. But with high carbon dioxide levels, the leaf stomata close slightly [stomata are crucial microstructures for gas exchange and transpiration found mainly in leaves that open during the day in the presence of light]. In other words, the plant captures the carbon dioxide it needs for its processes but loses less water. That's the protective effect CO₂ has against drought."
In the event of high temperatures and increased carbon dioxide in the environment, this would also prevent deleterious temperature effects and help the plant grow. "CO₂ generally increases the starch content in the leaf because, when it enters the plant and creates positive carbon pressure, the plant can't always completely process it, since that metabolism is very complex with numerous metabolic pathways. As the flow becomes congested, the plant begins to store carbon as a reserve in the form of leaf starch."
The question was, when the three effects are combined in a context closer to what would occur in the field, what happens to the bean? Buckeridge explains that the group focused on the seed because it is the main soybean product. "It's a very agriculture-focused study. I expected the three stress factors to cancel each other out, resulting in little change in plant growth. I was surprised that it grew more with all three stress factors. This means that temperature and high CO₂ are contributing to that effect since drought alone would cause the plant to produce less."
According to him, a lower starch content in the seed means that the plant directed the captured carbon toward building the cell wall, i.e., cellulose and hemicellulose, and produced more fiber. "In other words, high carbon dioxide causes a deviation from the normal metabolism of the bean. Drought causes a second deviation and temperature a third. When we combine the three, we get deviation number four. That means the process isn't linear, which is one of the most important findings from our latest published work. The pathways of the stress factors are different. Temperature and drought act through distinct stress pathways, metabolically speaking. We already understand that and have published it. That's why it's important to understand their effect in combination with high CO₂."
The work was supported by FAPESP through a Doctoral Scholarship and Research Internship Abroad awarded to the first author, Janaina da Silva Fortirer , as well as support from the Young PhD Retention Program awarded to Leandro Francisco de Oliveira , who is also an author of the article.
Experiment and modeling
When analyzed individually, increased carbon dioxide concentration raised bean production by up to 142%, while high temperatures and drought reduced yield by 91% and 60%, respectively. The combined triple effect (elevated CO₂ + high temperature + drought) was evaluated using predictive modeling based on dual-stress data that had been experimentally validated (elevated CO₂ + high temperature and elevated CO₂ + drought). However, the specific combination of these three factors was not experimentally validated.
"Conducting the experiment with all treatments and controls simultaneously would be a massive undertaking. We'd need to consider control groups for the combinations of high CO₂ with temperature and drought, high CO₂ with temperature but no drought, high CO₂ with drought only without temperature, and I don't have space in the system. I have chambers that raise the temperature, and I can create drought artificially by removing water from the plants. These experiments have already been tested and have yielded excellent results, allowing us to understand how different stresses affect plants separately and in combination," explains Buckeridge.
He is referring to open-top chambers, which are tubes with an open top into which carbon dioxide can be injected. The chambers are between 1.60 and 1.70 meters tall. "When they were built, all the calculations were done with engineers from USP's Engineering School to determine how long it takes for the CO₂ to enter and exit the chamber. In that experiment, we injected carbon dioxide so that the concentration inside would be twice the concentration in the ambient air [an average of 400 parts per million]. We therefore injected it so that there would be 800 ppm left."
The chambers read the ambient temperature and can raise it by up to 5 °C. "We put the plant under maximum stress, at the limit, with a temperature 5 °C higher and twice the CO₂, forcing it to respond." Finally, to simulate drought, the group stopped watering the plants. According to Buckeridge, they used a cultivar from the Brazilian Agricultural Research Corporation (EMBRAPA) called MG/BR-46 Conquista. It was "studied exhaustively because it's necessary to simulate a drought similar to real-world field conditions."
The plants were exposed to the following stress conditions, either individually or in combination: CO₂ and ambient temperature (400 ppm CO₂ + ambient temperature); high CO₂ (800 ppm CO₂ + ambient temperature); high temperature (400 ppm CO₂ + 5 °C); high CO₂ and high temperature (800 ppm CO₂ + 5 °C); drought (400 ppm CO₂ + reduced irrigation); and high CO₂ plus drought (800 ppm CO₂ + reduced irrigation). Total biomass, measured 60 days after the experiment began, was used to predict bean yield at 125 days.
To project the triple impact, the scientists used AI tools fed by the results of the experiments. Generalized linear models (GLMs) were applied to estimate the effects of the factors, both individually and in combination. With support from USP's Institute of Mathematical and Computational Sciences (ICMC), machine learning approaches (XGBoost and CatBoost) were used to predict the triple effect. "AI modeling was able to predict the results of two stress factors on the bean, as verified in the experiment. That leads us to believe that we can also rely on the results obtained from the modeling for the triple impact."
Mechanisms
According to the LAFIECO coordinator, the group's next step is to identify the genes responsible for the responses to the different stress factors and determine how these factors affect plant metabolism. "With that knowledge, we'll be able to redesign the plant to produce the same amount of protein while losing less starch, for example. Ultimately, it'll be possible to prepare the seed for better adaptation to climate change."
The scientists also aim to understand how these new parameters affect models used to predict the impact of climate change on crops. "It's likely that other species will behave similarly. We've already conducted the dual-effect experiment on sugarcane. Now, we need to test temperature and run the simulation using AI," Buckeridge explains.
About São Paulo Research Foundation (FAPESP)
The São Paulo Research Foundation (FAPESP) is a public institution with the mission of supporting scientific research in all fields of knowledge by awarding scholarships, fellowships and grants to investigators linked with higher education and research institutions in the State of São Paulo, Brazil. FAPESP is aware that the very best research can only be done by working with the best researchers internationally. Therefore, it has established partnerships with funding agencies, higher education, private companies, and research organizations in other countries known for the quality of their research and has been encouraging scientists funded by its grants to further develop their international collaboration. You can learn more about FAPESP at www.fapesp.br/en and visit FAPESP news agency at www.agencia.fapesp.br/en to keep updated with the latest scientific breakthroughs FAPESP helps achieve through its many programs, awards and research centers. You may also subscribe to FAPESP news agency at http://agencia.fapesp.br/subscribe
