Research Newly Discovered Carbon Pathway Could Explain Faster Plant Growth Under Rising CO2 Concentrations

16 December 2024

When plants take up carbon dioxide (CO₂), they use light to convert the carbon atoms into various molecules. The carbon atoms help, for example, manufacture proteins and structural substances that enhance cell growth and plant structure. These biochemical processes are known as “pathways”. The carbon pathway now detected for the first time in California poplar trees stems from the so-called C₁ photosynthesis reaction that plants use to make oxygen and organic compounds. In the process, molecules with one carbon atom (C₁) are transferred. The carbon pathway was discovered by scientists from the Earth Environmental Sciences Area at the Lawrence Berkeley National Laboratory (USA) in collaboration with Prof. Dr Frank Keppler, who heads the Biogeochemistry research group at the Institute of Earth Sciences of Heidelberg University. 

The team studied how the leaves of the California poplar use carbon and allocate the carbon atoms in the plant during photosynthesis. To do this, the researchers labeled CO₂ with heavy (¹³C) carbon isotopes. Prof. Keppler in Heidelberg then analyzed how the isotopes circulated in the plant. The measurements show that the newly found carbon pathway takes on a key function in the fast transport of atoms during photosynthesis. A chemical reaction known as methylation ensures that the carbon atoms reach their various destinations, where they are needed to build cells, carbohydrates, proteins, and structural substances like pectin required for plant growth. 

Based on similar observations of other photosynthetic processes, the scientists assume that the carbon pathway they identified will have a greater impact under CO₂ concentrations that continue to increase steadily, also driving climate change. This could cause plants to grow more quickly in future. The researchers hope that these new findings on the carbon cycle in plants might point to how well forests will respond to climate change and rising carbon dioxide concentrations in future. 

“This newfound carbon pathway could also prove to be crucial in better understanding the plant-based release of climate-relevant gases,” adds Frank Keppler. During the C₁ photosynthesis reaction, the geoscientist explains, the amino acid methionine develops, which helps build proteins but has also been linked to the production of the greenhouse gas methane and other climate-related C₁ gases such as chloromethane and methanol. Earlier studies concluded that plants only transport methane generated by soil microbes. The current study, however, supports the hypothesis that methane, chloromethane, and methanol could form via methionine metabolism in plants. According to Prof. Keppler, this would suggest that methane is also synthesized directly in photosynthetic tissues.

In addition to scientists from Berkeley and Heidelberg, researchers from the University of California at Berkeley, the Australian National University, and the University of São Paolo (Brazil) also contributed to the work. The results of the research were published in the journal “Communications Biology”.