Crops with boosted photosynthesis

In plain language

Plants make food from sunlight, water and carbon dioxide. Two things often slow this down. When a cloud or a neighbouring leaf passes over, a leaf keeps its protective heat release switched on for minutes, so it stays slow to photosynthesise when full sun returns. Also, the main carbon-fixing enzyme, Rubisco, sometimes takes up oxygen instead of carbon dioxide, and the plant then spends energy recycling the mistake. This loss is called photorespiration.

Researchers are trying to change one or both of these processes in food crops. Tobacco has been the easiest test plant. Field trials in tobacco and rice, and one in soybean, report gains in biomass or grain. These results are early, but they come from a small number of experiments, one soybean result has been publicly challenged, and no crop has yet been shown to deliver the same gain across many sites and seasons.

Technical explanation

Photorespiration begins when Rubisco fixes oxygen rather than carbon dioxide, producing 2-phosphoglycolate. In the native pathway, carbon is released as carbon dioxide and nitrogen is lost as ammonia, and the plant spends energy to recover the rest. South and colleagues (2019) built synthetic glycolate metabolism pathways in tobacco chloroplasts, and some lines also used an RNAi module to limit glycolate export from the chloroplast so that more flux passed through the new route. They reported a 20% gain in photosynthetic quantum yield, and their replicated field trials in tobacco in 2016 and 2017 are the basis for the biomass figures reported below.

A separate strategy targets non-photochemical quenching, the protective heat dissipation controlled partly by the xanthophyll cycle. Kromdijk and colleagues (2016) sped up the cycle and raised a photosystem II subunit in tobacco, reporting about 15% higher dry matter productivity in fluctuating light. De Souza and colleagues (2022) moved the same approach into soybean and reported that replicated field trials showed higher photosynthetic efficiency in fluctuating light, with seed yield up to 33% higher across five independent transformation events and unchanged protein and oil content. A Science comment by Sinclair and colleagues (2023) disputes whether the field experiment supports a yield increase. The 2019 tobacco study was corrected by an erratum published in August 2019. The erratum text was not read in full for this review, so its statistical detail is not stated here.

In rice, Chen and colleagues (2025) designed a carbon and nitrogen metabolism-coupled bypass, reporting an average 19.0% yield increase (17.8% to 20.2%) over wild type under natural growth conditions, and a 44.1% offset of yield losses under nitrogen-limited conditions. The abstract does not say whether these were field trials. The Results section of the full paper describes field-grown plants, so the setting is field-based, but the nitrogen-limited figures in the body text differ from the abstract and should be checked against the full paper before comparing them with the field data above.

What the evidence says

Each statement is typed by the strength of its evidence and linked to the source that supports it.

Limitations and open problems

• The soybean yield claim (up to 33% seed yield in five transformation events) has been challenged in a published Science comment (Sinclair and colleagues, 2023), which argues that the field experiment does not provide evidence for a yield increase.
• The 2019 tobacco field study was corrected by an erratum published in August 2019. The erratum text was not read in full for this review, so the effect of the correction on the reported biomass gains is not stated here.
• Most reported gains come from tobacco, a model plant, or from one soybean study. Replication across independent sites, seasons and commercial germplasm has not been shown in the sources reviewed.
• The rice result (Chen and colleagues, 2025) is reported under natural growth conditions. The abstract does not say whether it is a field trial. Nitrogen-limited gains are reported separately and are not the same as yield gains under good nitrogen supply, and the nitrogen-limited figures in the body text differ from the abstract.
• Yield gains in engineered crops depend on the environment. Kromdijk and colleagues (2016) describe the benefit as seen in fluctuating light, so gains may be smaller or absent in stable, full-sun conditions.
• Regulatory status for field release of these transgenic crops in any country was not verified in the sources reviewed, so it is not stated here.

Possible future uses

Timeline

1. Nov 2016Kromdijk and colleagues report faster recovery from photoprotection in tobacco, with about 15% higher dry matter productivity in fluctuating light. Sources: [1]
2. 4 Jan 2019South and colleagues report synthetic glycolate pathways in tobacco with a 20% gain in photosynthetic quantum yield and biomass gains in replicated field trials in 2016 and 2017. Sources: [4]
3. 2 Aug 2019Science publishes an erratum to the 2019 field study. Sources: [5]
4. 18 Aug 2022De Souza and colleagues report replicated field trials of engineered soybean, with seed yield up to 33% higher in five independent transformation events and unchanged protein and oil content. Sources: [2]
5. 24 Feb 2023A Science comment by Sinclair and colleagues disputes the yield claim from the soybean field experiment. Sources: [3]
6. Jan 2025Chen and colleagues report a synthetic photorespiratory bypass in rice with an average 19.0% yield increase under natural growth conditions. Sources: [6]

Futures this could help bring about

How far away?

Crops that keep yielding in drought

Scaling up · 3 of 7 steps done

Related breakthroughs

• Soybean lines with faster recovery from light protection yielded up to 33% more seed in field trials (18 Aug 2022)

Glossary

Photorespiration

A process in which Rubisco takes up oxygen instead of carbon dioxide, so the plant loses carbon and spends energy recovering it.

Rubisco

The enzyme that fixes carbon dioxide into sugar precursors in photosynthesis; it can also react with oxygen.

Non-photochemical quenching

The protective release of excess absorbed light as heat in leaves, which slows photosynthesis when light falls suddenly.

Quantum yield

The efficiency with which absorbed light is used for photosynthesis, usually reported as a ratio of products to photons.

Sources

1. peer reviewed paper
   Improving photosynthesis and crop productivity by accelerating recovery from photoprotection
   Kromdijk J, Głowacka K, Leonelli L et al.. Science, Nov 2016. DOI: 10.1126/science.aai8878. Accessed 22 Oct 2026.
2. peer reviewed paper
   Soybean photosynthesis and crop yield are improved by accelerating recovery from photoprotection
   De Souza AP, Burgess SJ, Doran L et al.. Science, 18 Aug 2022. DOI: 10.1126/science.adc9831. Accessed 22 Oct 2026.
3. peer reviewed paper
   Comment on "Soybean photosynthesis and crop yield are improved by accelerating recovery from photoprotection"
   Thomas Sinclair, James Specht, Kenneth Cassman et al.. Science, 24 Feb 2023. DOI: 10.1126/science.ade8506. Accessed 22 Oct 2026.
4. peer reviewed papercorrected
   Synthetic glycolate metabolism pathways stimulate crop growth and productivity in the field
   Paul F. South, Amanda P. Cavanagh, Helen W. Liu et al.. Science, 4 Jan 2019. DOI: 10.1126/science.aat9077. Accessed 22 Oct 2026.
5. other
   Erratum for the Research Article "Synthetic glycolate metabolism pathways stimulate crop growth and productivity in the field"
   Science, 2 Aug 2019. DOI: 10.1126/science.aay8818. Accessed 22 Oct 2026.
6. peer reviewed paper
   Synthetic photorespiratory bypass improves rice productivity by enhancing photosynthesis and nitrogen uptake
   Guoxin Chen, Yanni Li, Kaining Jin et al.. The Plant Cell, Jan 2025. DOI: 10.1093/plcell/koaf015. Accessed 22 Oct 2026.

Revision history

3 changes since this profile was created.