What is it about?
Plants may need sunlight to photosynthesise, but they can still get ‘sunburnt’ – excess light can severely damage the photosynthetic machinery. To protect against light damage, plants use a process called nonphotochemical quenching (NPQ) to safely dissipate excess energy as heat. This study looks at plants with C4 photosynthesis, an adaptation of the C3 pathway that concentrates CO2 around the main carbon-fixing enzyme Rubisco, and finds that they turn off NPQ significantly faster than C3 plants. Whilst turning on NPQ in response to intense light is important, so is turning it off in the shade, where light is in short supply and delays in NPQ deactivation limit photosynthesis. C4 plants (like corn or sorghum) are well-known to have higher photosynthetic rates than C3 plants (like rice or soy), and faster NPQ represents an additional advantage that adds up in the ever-changing light environments plants grow in.
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Why is it important?
NPQ is a crucial process, yet most of what we know about it comes from plants with C3 photosynthesis. Our experiments show that this important photoprotective response is fundamentally different between photosynthetic pathways and shaped by the specific energy requirements of C3 and C4 photosynthesis, with implications for how we approach improving photosynthesis under changing light.
Perspectives
Most familiar C3 and C4 species are separated by millions of years of evolution, which makes comparing anything between photosynthetic pathways quite difficult. Are differences in NPQ due to the C4 pathway, or simply species variation? We tackled this problem by working with three pairs of the only C3 and C4 species in the same phylogenetic genera. The results were striking – in every comparison, C4 plants relaxed NPQ faster than their C3 relatives, a result further supported by a metanalysis across diverse plant species. I think C4 photosynthesis is an incredible feat of evolution, and there is still so much more to learn about this adaptation.
Lucía Arce Cubas
University of Illinois at Urbana-Champaign
Read the Original
This page is a summary of: Faster relaxation of nonphotochemical quenching in C4 than in C3 species, Proceedings of the National Academy of Sciences, September 2026, Proceedings of the National Academy of Sciences,
DOI: 10.1073/pnas.2621033123.
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