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Crop Biotech Update

Adapting Photosynthesis to Fleeting Shadows Boosts Soybean Yields

February 26, 2020

It is a known fact that crops harness light energy to fix carbon dioxide into food via photosynthesis. A team from the University of Illinois has reported a new mathematical model that is used to understand how much yield is lost as soybean crops grapple with minute-by-minute light fluctuations on cloudy and sunny days.

Yu Wang, a postdoctoral researcher at Illinois working for Realizing Increased Photosynthetic Efficiency (RIPE) said soybean is the fourth most important crop in terms of overall production, but it is the top source of vegetable protein globally. "We found that soybean plants may lose as much as 13 percent of their productivity because they cannot adjust quickly enough to the changes in light intensity that are standard in any crop field." The team created a dynamic computational ray-tracing model that predicts light levels to the millimeter across every leaf for every minute of the day in a flowering soybean crop. The model also takes into account two critical factors: photoprotection and Rubisco activase.

Photoprotection protects plants from sun damage. This process is triggered by high light levels and dissipates excess light energy safely as heat. When light levels drop, it takes minutes to hours for photoprotection to relax, or stop—costing the plant potential yield. The team evaluated 41 varieties of soybean to find out the fastest, slowest, and average rate from induction to the relaxation of photoprotection. Less than 30 minutes is considered "short-term," and anything longer is "long-term" photoprotection.

The team also simulated a sunny and cloudy day in Champaign, Illinois. On sunny days, long-term photoprotection was the most significant limitation of photosynthesis. On a cloudy day, photosynthesis was the most limited by short-term photoprotection and Rubisco activase, which is a helper enzyme—triggered by light—that turns on Rubisco to fix carbon into sugar.

For more details, read the news release from the University of Illinois.

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