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Cassava yields could benefit from rising CO2 levels in the atmosphere

Cassava yields could benefit from rising CO2 levels in the atmosphere
An aerial photograph reveals several experimental plots of cassava crops at the University of Illinois SoyFACE research facility. Photo by Beau Barber/RIPE project

Nov. 11 (UPI) -- Cassava, a root crop that feeds more than 1 billion people around the world, could benefit from rising atmospheric CO2 levels.

In a new study, published recently in the Journal of Experimental Botany, scientists artificially boosted the CO2 supply of cassava plants planted at SoyFACE, Soybean Free Air Concentration Enrichment, a research farm in Illinois.

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The experiment -- part of an ongoing Bill & Melinda Gates Foundation-funded effort to enhance photosynthesis to boost crop yields -- showed cassava plants are likely to benefit from higher concentrations of atmospheric carbon.

In seven of the eight planted cassava varieties, researchers found enhanced CO2 levels boosted yields between 22 to 39 percent.

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"These results suggest that higher cassava yields can be expected as atmospheric [CO2] increases over the coming decades," researchers wrote.

Scientists have previously estimated that a variety of crops might benefit from rising CO2 levels.

Studies have also shown that the efficiency with which crops can translate higher CO2 levels and accelerated photosynthesis rates into enhanced yields can depend on a variety of other factors, including temperature and water availability.

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Previous studies have also shown that higher CO2 levels and accelerated photosynthesis rates can boost crop yields but depress nutrient levels.

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The latest experiments showed, however, that cassava roots can benefit from elevated CO2 levels without sacrificing nutritional quality.

"We wanted to know how cassava copes with elevated carbon dioxide," study co-author Donald Ort said in a news release.

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"Sometimes, plants cannot make use of extra carbohydrates, which then triggers the plant to down-regulate photosynthesis. We found cassava could maintain photosynthetic efficiency and nutritional quality," said Ort, a professor of crop sciences and plant biology at the University of Illinois' Carl R. Woese Institute for Genomic Biology.

Plants open their pores to take in CO2. When they do, water escapes into the atmosphere -- a phenomenon known as transpiration.

Higher levels of CO2 allowed cassava to take in carbon without losing as much water. Increases in CO2 levels from 400 to 600 parts per million corresponded with a 58 percent improvement in water conservation.

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"Cassava's natural ability to produce high yields with little water is part of what makes this crop a staple in drought-prone regions across sub-Saharan Africa," said co-author Amanda De Souza.

"It is not surprising to see this trait magnified in C3 crops, but it is encouraging since we predict water scarcity to be a major barrier to food security," said De Souza, a postdoctoral researcher for the RIPE project at Illinois.

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Among the eight cassava varieties, researchers found there were differences in how the plants allocated surplus carbohydrates to their roots, stems and leaves, a process called partitioning.

"We can capitalize on these differences in partitioning to develop cassava varieties that sink more carbon into their roots to boost yields," said lead author Ursula Ruiz Vera.

"We aim to enhance the natural resilience and productivity of this crop that is uniquely situated to help smallholder farmers withstand pressures from our changing climate," said Ruiz Vera, a postdoctoral researcher at Illinois.

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