Corn and other crops are not adapted to benefit from elevated carbon dioxide levels

November 05, 2020

The U.S. backs out of the Paris climate agreement even as carbon dioxide (CO2) levels continue to rise. Through photosynthesis, plants are able to turn CO2 into yield. Logic tells us that more CO2 should boost crop production, but a new review from the University of Illinois shows that some crops, including corn, are adapted to a pre-industrial environment and cannot distribute their resources effectively to take advantage of extra CO2.

Most plants (including soybeans, rice, canola, and all trees) are C3 because they fix CO2 first into a carbohydrate containing three carbon atoms. Corn, sorghum, and sugarcane belong to a special group of plants known as C4, so-called because they first fix CO2 into a four-carbon carbohydrate during photosynthesis. On average, C4 crops are 60 percent more productive than C3 crops.

When crops are grown in elevated CO2 that mimic future atmospheric conditions, research shows that C3 crops can become more productive while some experiments suggest that C4 crops would be no more productive in a higher CO2 world.

"As scientists, we need to think several steps ahead to anticipate what the Earth will look like five to 30 years from now, and how we can design crops to perform well under those conditions," said Charles Pignon, a former postdoctoral researcher at Illinois. "We decided that a literature review and a retrospective analysis of biochemical limitations in photosynthesis would be able to give us some insight into why C4 crops might not respond and how we might alter this."

The literature review, published in Plant, Cell & Environment, was supported by Water Efficient Sorghum Technologies (WEST), a research project that aimed to develop bioenergy crops that produce more biomass with less water, with funding from the Advanced Research Projects Agency-Energy (ARPA-E).

The team assembled a dataset of photosynthesis measurements from 49 C4 species, including the crops that could reveal photosynthetic limitations. The consistent pattern that emerged was that at low CO2--well below what plants would have experienced before the industrial revolution--C4 photosynthesis was limited by the activity of the enzyme that fixes CO2. However, at today's CO2 levels, C4 photosynthesis was limited by the capacity to provide the three-carbon molecule that accepts the fourth CO2.

"This finding is analogous to a car assembly line where the supply of engines is outpacing the supply of chassis to accept them," said co-author Stephen Long, the Stanley O. Ikenberry Chair Professor of Plant Biology and Crop Sciences. "We need to engineer these plants to better balance their resources in one or both of two-ways."

First, the authors suggest that C4 crops need to cut back on the amount of the enzyme used to fix CO2 and re-invest the saved resources into making more of the CO2 acceptor molecule.

Secondly, they need to restrict the supply of CO2 into the leaf by reducing the number of pores (stomata) on the leaf surface. "Lowering the CO2 within the leaf would re-optimize the biochemistry, without lowering the rate of photosynthesis, and with fewer stomata, less water would be lost so we are increasing the crop's water use efficiency," Long said.

The WEST project concluded in 2019. These proposed changes to C4 crops are now being pursued through the Center for Advanced Bioenergy and Bioproducts Innovation (CABBI), which is supported by the Department of Energy.
-end-
Water Efficient Sorghum Technologies (WEST) was a research project that helped develop bioenergy crops that require less water per acre to ensure a sustainable source of biofuel. The project was supported by the Advanced Research Projects Agency-Energy and led by the University of Illinois in partnership with Cornell University, University of Nebraska-Lincoln, University of Wisconsin-Madison, and the USDA Agricultural Research Service.

Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign

Related Photosynthesis Articles from Brightsurf:

During COVID, scientists turn to computers to understand C4 photosynthesis
When COVID closed down their lab, a team from the University of Essex turned to computational approaches to understand what makes some plants better adapted to transform light and carbon dioxide into yield through photosynthesis.

E. coli bacteria offer path to improving photosynthesis
Cornell University scientists have engineered a key plant enzyme and introduced it in Escherichia coli bacteria in order to create an optimal experimental environment for studying how to speed up photosynthesis, a holy grail for improving crop yields.

Showtime for photosynthesis
Using a unique combination of nanoscale imaging and chemical analysis, an international team of researchers has revealed a key step in the molecular mechanism behind the water splitting reaction of photosynthesis, a finding that could help inform the design of renewable energy technology.

Photosynthesis in a droplet
Researchers develop an artificial chloroplast.

Even bacteria need their space: Squished cells may shut down photosynthesis
Introverts take heart: When cells, like some people, get too squished, they can go into defense mode, even shutting down photosynthesis.

Marine cyanobacteria do not survive solely on photosynthesis
The University of Cordoba published a study in a journal from the Nature group that supports the idea that marine cyanobacteria also incorporate organic compounds from the environment.

Photosynthesis -- living laboratories
Ludwig-Maximilians-Universitaet (LMU) in Munich biologists Marcel Dann and Dario Leister have demonstrated for the first time that cyanobacteria and plants employ similar mechanisms and key proteins to regulate cyclic electron flow during photosynthesis.

Photosynthesis seen in a new light by rapid X-ray pulses
In a new study, led by Petra Fromme and Nadia Zatsepin at the Biodesign Center for Applied Structural Discovery, the School of Molecular Sciences and the Department of Physics at ASU, researchers investigated the structure of Photosystem I (PSI) with ultrashort X-ray pulses at the European X-ray Free Electron Laser (EuXFEL), located in Hamburg, Germany.

Photosynthesis olympics: can the best wheat varieties be even better?
Scientists have put elite wheat varieties through a sort of 'Photosynthesis Olympics' to find which varieties have the best performing photosynthesis.

Strange bacteria hint at ancient origin of photosynthesis
Structures inside rare bacteria are similar to those that power photosynthesis in plants today, suggesting the process is older than assumed.

Read More: Photosynthesis News and Photosynthesis Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.